Quite honestly, I don't think this is necessarily parasites at all, and automatically medicating him with a harsh medication is not the right answer anyway, at all costs you should always try to NOT give your Dragon medications. Smelly bowel movements are NOT always a sign of parasites at all, and runny or watery bowel movements are caused by a million different reasons, so don't yourself hung-up on "He definitely has parasites", or even if he does have parasites, that doesn't mean he needs medicine...
The questions you need to be asking yourself are #1) Is he eating normally, is his appetite normal? and #2) Is he at all lethargic, sleeping a lot more than usual, or avoiding his lights? IF the answer to either of these questions is No, then he most likely doesn't have a high-enough parasitic count that he needs a medication.
The two most common parasites that Dragons get are #1) Pinworms, which is usually treated with Panacur, and #2) Coccidia, which are Protozoa, and should be treated with Toltrazuril (never allow your Dragon to be given Albon for Coccidia, it's a Sulfa Drug that makes that not only is ineffective and usually takes multiple rounds, but makes them very sick)...
Bearded Dragons, all Dragons, at any given time, usually have one or the other of these two parasites throughout their GI Tracts in low to moderate counts/loads, and even so the Dragons are just fine. This is because if your Dragon is healthy then his Immune System will keep these in-check. If you told me that your Dragon had lost his appetite, wasn't eating normally or at all, and was very lethargic, sleeping more than usual and not basking, then I would tell you that he needs a fecal test because he may have a parasitic infection in High Counts, and probably needs to be medicated...But that's not the situation I don't think, doesn't sound like it. And it's also important to know that Panacur does not "kill" Pnworms, it simply makes the females sterile and then serves to flush them from their GI Tracts, which you can accomplish at home with some fiber and herbs. And if he had a high level of Coccidia, he'd most likely not be eating and he'd be acting like he's sickly.
*****Very important misconception that you wrote, about his "stress marks", by this I'm assuming that you're talking about the markings on his belly...Well that's exactly what they are, that's ALL they are, they are markings on his belly, just like the rest of the markings all over his body. They do not at all represent "stress" or anything else, other than he's darkening himself because he's trying to absorb more light/heat. If you haven't yet noticed, when you Dragon is inside his tank, that's typically when his colors are darker, and when you take him out of his tank he immediately lightens right up, unless you put him near a window or outside in the sun. That's because he has lights over his tank and he's trying to absorb as much light/heat as he can. But when you take him out of his tank there are no longer lights, so he doesn't need to be dark anymore...And also, when he gets a warm bath he's probably very light, that's because he's very warm from the water and needs no more heat. So the bottom line to this point is 2 things: #1) He has no "stress marks" at all, that's an internet myth, the same as "they absorb water/hydration through their vents and/or their skin/scales by soaking in water", that's totally untrue as well, they only get hydration the way we do, through their mouths....and then #2) My guess is that his Basking Spot Surface Temperature, which absolutely CANNOT BE MEASURED with any type of Stick-On Thermometer, is probably too low!
Do you have either a Temperature Gun or a Digital Thermometer with a Probe on a Wire to measure his Basking Spot Temperature with? If he's under a year old, then his Basking Spot Surface Temperature must be between 105-110 degrees F, and if he's a year old or older it must be between 100-105 degrees F, or he cannot properly digest his food, nor will he have normal bowel movements...This may very well be the reason he's having the bowel movements he is, that and he's eating a lot of veggies/greens and fruits, especially the fruits you are feeding him. So if you are relying on only a Stick-On Thermometer that is located in the Hot Side of his tank, then that is not at all his Basking Spot Temperature that you're reading, but rather his Hot Side Air/Ambient Temperature, which should be between 88-93 degrees F. So if you're actually reading higher than 93 degrees F on a Stick-On Thermometer in the Hot Side of his tank, that means that his temperature zones are way too hot, because naturally the Surface Temperature of his basking spot/platform is going to be higher than the Hot Side Air Temperature surrounding it...This can cause as many issues as having a Basking Spot Surface Temperature that is too low can, such as severe Dehydration, Heat Exhaustion, and permanent issues regulating their body temperature. So the bottom line is that if you are only using Stick-On Thermometers, you absolutely must spend $10 at any Petco or really any pet store and buy a Digital Thermometer that has a Probe on a Wire, and you must set the Probe directly on his Basking Spot/Platform (that should be located within the Hot Side of his tank, directly underneath both his UVB tube and his bright-white colored Basking Bulb). Allow the Probe to sit on the Basking Platform for at least 20 minutes, or until the temperature on the Digital Thermometer stops rising...THIS IS THE ACTUAL BASKING SPOT SURFACE TEMPERATURE, WHICH NEEDS TO BE BETWEEN 100-105 DEGREES F IF HE'S OVER A YEAR OLD...*******This is not optional when owning a Desert Reptile, and is a much better use of money than ordering parasitic medications online that he most likely doesn't need.
*****Fruit is nothing but water and sugar, and sugar is very bad for Dragons, so if you're giving him any fruit more than twice a week than you definitely need to cut that back, this is contributing to the runny, watery, smelly bowel movements for sure. The other BIG issue is giving him 6 or 7 Superworms in one sitting, that's WAY TOO MANY SUPERWORMS!!! These are his problems, his diet and temperature zones, not parasites! Superworms are NOT a "Staple" Feeder Insect, they are loaded, absolutely loaded with fat, and if you're giving him 6 or 7 Superworms at one time this is absolutely going to mess up his bowel movements. You need to be feeding him either Crickets, Dubia Roaches or another species of Roaches, Phoenix Worms/BSFL/NutriGrubs/CalciWorms/ReptiWorms (all the same thing, just different Brand Names), or SilkWorms as his regular, daily live insects. At most you should only give him 1 or 2 Superworms as a SUPPLEMENT to the healthy, Staple Insect that is high in Protein and low in Fat....Not only is feeding him so many Superworms causing the bowel movement issues, but he's very likely going to end-up with Fatty Liver Disease very young if you don't stop it soon...
So these are the things you need to correct FIRST, before medicating him for parasites that he likely doesn't need to be medicated for....
The questions you need to be asking yourself are #1) Is he eating normally, is his appetite normal? and #2) Is he at all lethargic, sleeping a lot more than usual, or avoiding his lights? IF the answer to either of these questions is No, then he most likely doesn't have a high-enough parasitic count that he needs a medication.
The two most common parasites that Dragons get are #1) Pinworms, which is usually treated with Panacur, and #2) Coccidia, which are Protozoa, and should be treated with Toltrazuril (never allow your Dragon to be given Albon for Coccidia, it's a Sulfa Drug that makes that not only is ineffective and usually takes multiple rounds, but makes them very sick)...
Bearded Dragons, all Dragons, at any given time, usually have one or the other of these two parasites throughout their GI Tracts in low to moderate counts/loads, and even so the Dragons are just fine. This is because if your Dragon is healthy then his Immune System will keep these in-check. If you told me that your Dragon had lost his appetite, wasn't eating normally or at all, and was very lethargic, sleeping more than usual and not basking, then I would tell you that he needs a fecal test because he may have a parasitic infection in High Counts, and probably needs to be medicated...But that's not the situation I don't think, doesn't sound like it. And it's also important to know that Panacur does not "kill" Pnworms, it simply makes the females sterile and then serves to flush them from their GI Tracts, which you can accomplish at home with some fiber and herbs. And if he had a high level of Coccidia, he'd most likely not be eating and he'd be acting like he's sickly.
*****Very important misconception that you wrote, about his "stress marks", by this I'm assuming that you're talking about the markings on his belly...Well that's exactly what they are, that's ALL they are, they are markings on his belly, just like the rest of the markings all over his body. They do not at all represent "stress" or anything else, other than he's darkening himself because he's trying to absorb more light/heat. If you haven't yet noticed, when you Dragon is inside his tank, that's typically when his colors are darker, and when you take him out of his tank he immediately lightens right up, unless you put him near a window or outside in the sun. That's because he has lights over his tank and he's trying to absorb as much light/heat as he can. But when you take him out of his tank there are no longer lights, so he doesn't need to be dark anymore...And also, when he gets a warm bath he's probably very light, that's because he's very warm from the water and needs no more heat. So the bottom line to this point is 2 things: #1) He has no "stress marks" at all, that's an internet myth, the same as "they absorb water/hydration through their vents and/or their skin/scales by soaking in water", that's totally untrue as well, they only get hydration the way we do, through their mouths....and then #2) My guess is that his Basking Spot Surface Temperature, which absolutely CANNOT BE MEASURED with any type of Stick-On Thermometer, is probably too low!
Do you have either a Temperature Gun or a Digital Thermometer with a Probe on a Wire to measure his Basking Spot Temperature with? If he's under a year old, then his Basking Spot Surface Temperature must be between 105-110 degrees F, and if he's a year old or older it must be between 100-105 degrees F, or he cannot properly digest his food, nor will he have normal bowel movements...This may very well be the reason he's having the bowel movements he is, that and he's eating a lot of veggies/greens and fruits, especially the fruits you are feeding him. So if you are relying on only a Stick-On Thermometer that is located in the Hot Side of his tank, then that is not at all his Basking Spot Temperature that you're reading, but rather his Hot Side Air/Ambient Temperature, which should be between 88-93 degrees F. So if you're actually reading higher than 93 degrees F on a Stick-On Thermometer in the Hot Side of his tank, that means that his temperature zones are way too hot, because naturally the Surface Temperature of his basking spot/platform is going to be higher than the Hot Side Air Temperature surrounding it...This can cause as many issues as having a Basking Spot Surface Temperature that is too low can, such as severe Dehydration, Heat Exhaustion, and permanent issues regulating their body temperature. So the bottom line is that if you are only using Stick-On Thermometers, you absolutely must spend $10 at any Petco or really any pet store and buy a Digital Thermometer that has a Probe on a Wire, and you must set the Probe directly on his Basking Spot/Platform (that should be located within the Hot Side of his tank, directly underneath both his UVB tube and his bright-white colored Basking Bulb). Allow the Probe to sit on the Basking Platform for at least 20 minutes, or until the temperature on the Digital Thermometer stops rising...THIS IS THE ACTUAL BASKING SPOT SURFACE TEMPERATURE, WHICH NEEDS TO BE BETWEEN 100-105 DEGREES F IF HE'S OVER A YEAR OLD...*******This is not optional when owning a Desert Reptile, and is a much better use of money than ordering parasitic medications online that he most likely doesn't need.
*****Fruit is nothing but water and sugar, and sugar is very bad for Dragons, so if you're giving him any fruit more than twice a week than you definitely need to cut that back, this is contributing to the runny, watery, smelly bowel movements for sure. The other BIG issue is giving him 6 or 7 Superworms in one sitting, that's WAY TOO MANY SUPERWORMS!!! These are his problems, his diet and temperature zones, not parasites! Superworms are NOT a "Staple" Feeder Insect, they are loaded, absolutely loaded with fat, and if you're giving him 6 or 7 Superworms at one time this is absolutely going to mess up his bowel movements. You need to be feeding him either Crickets, Dubia Roaches or another species of Roaches, Phoenix Worms/BSFL/NutriGrubs/CalciWorms/ReptiWorms (all the same thing, just different Brand Names), or SilkWorms as his regular, daily live insects. At most you should only give him 1 or 2 Superworms as a SUPPLEMENT to the healthy, Staple Insect that is high in Protein and low in Fat....Not only is feeding him so many Superworms causing the bowel movement issues, but he's very likely going to end-up with Fatty Liver Disease very young if you don't stop it soon...
So these are the things you need to correct FIRST, before medicating him for parasites that he likely doesn't need to be medicated for....