Welcome to the forum! Don't stress too much, this is very common, unfortunately the pet shops don't have a clue what they're talking about..
You've gotten good information, no night light at all, none, they sleep most comfortably when it is pitch-black and cool at night, just like the Australian Desert they are from.
You need a $10 Digital Probe Thermometer ASAP, and this will allow you to measure his Basking Spot Surface Temperature, which should be between 105-110 degrees F, Hot Side Air Temp between 88-93 degrees F, and the Cool Side Air Temp between 75-80 degrees F. The wattage of the Basking Bulb you have is determined by what wattage with get these 3 temps within the correct ranges. ONLY USE A BRIGHT-WHITE COLORED BASKING BULB! NO RED, BLUE, ETC.
The 22" or longer Reptisun 10.0 T5HO UVB tube can be purchased on Amazon.com for around $24 (BE SURE NOT TO BUY THE 5.0 VERSION, DRAGONS NEED 10% OR 10.0
UVB LIGHT). Amazon.com also sells a 24" T5-rated tube fixture with a reflector inside it for $28. THIS IS NOT OPTIONAL, IT'S THE MOST IMPORTANT THING YOU WILL EVER BUY FOR YOUR BEARDIE! Be sure that both the UVB tube and the bright-white colored Basking Bulb must be on each day for at least 13-14 hours. Please get the UVB tube and fixture immediately, this is a big deal, he cannot absorb any nutrition at all without a proper UVB tube, and will develop MBD.
As far as his diet goes, I suggest that you start ordering his live insects online in bulk, because you'll save a fortune. Dragons from the time they hatch until they are about a year old eat tons and tons of live insects every single day, usually on average they will be eating between 40-60 live insects each day.
They typically don't eat much if any greens/veggies until they are around a year old, when they will eventually switch themselves over from tons of insects to tons of salad. However, you must offer him a fresh salad every day so that he gets used to eating it.
******We usually tell people that a Dragon from hatching to a year old needs at least 2 live insect feeding sessions every single day, though 3 sessions is better. Each session should last between 10-15 minutes, where he is allowed to eat as many live insects as he wants to. The appropriate Dragon live staple insects are Crickets, Roaches, Silkworms, or BSFL/Phoenix Worms. You're much better off buying a large, plastic tub from Walmart or somewhere and then buying your live insects in bulk, because as I said, he'll be eating a ton of them every day.
Dragons due most all of their growing and developing during their first year of life, which is why they need all of the live insect protein during year one. For example, I feed size Large BSFL as my live staple insect. I order 1,000 a month from
www.dubiaroaches.com for about $24 shipped. Crickets and roaches are less. Usually my young guy will eat 20 in the morning, 15 in the afternoon, and then 10-15 in the evening. So it's really much more affordable to order them online in bulk than running to a pet shop every day.
Make sure you dust all of the live insects from one daily feeding session (not all the daily feeding sessions, just all of the insects from one) in a calcium powder 5 days a week, and then the same with a Reptile Multivitamin 3 days a week.
DO NOT WASTE YOUR MONEY ON THE INSECT/CRICKET FEED OR
HYDRATION CUBES AT THE PET SHOP!!! First of all, all of those "
Hydration Gels" or cubes are made out of the same stuff they make those gel beads that you put into potted plants to keep them watered. It's terrible stuff, and a waste of money, as are the Bearded Dragon pellets. And never buy any freeze-dried insects to feed him. Dragons don't often drink water from a bowl or the
bath, as they really have no concept of standing water since there isn't much in the Australian Desert. So most Dragons get most of their
hydration from the tons of live insects they eat when they are young, and then from the tons of fresh greens/veggies when they are older.
To keep your live insects, just simply throw in a couple of handfuls of the same, fresh greens and veggies you offer him into the live insect tub, along with a few peeled apple slices for their water. That's it. Do not waste money buying any "commercial" foods for either your beardie or your live insects, it's not necessary and it's unhealthy for them both.
I just wanted to reiterate that the tail has some trauma that caused it to die on the end. It will probably fall off at some point but may linger for a while. Pay special attention that any infection doesn't spread upwards at all. That would be active necrosis or tail rot and would require amputation. So be really watchful, tail rot can be very serious.
