Well first of all, don't you ever hesitate to ask any questions you every have, and you tell your son the same thing! That's why we're all here, we want to help all of the loving, caring, well-meaning Beardie owners who only followed the advice given to them by pet shop employees who they should have no reason at all not to trust. I'm glad your son is handling it well, that's tough for anyone, let alone an 8 year-old, but you're absolutely correct, now you know so much more, you have all the correct lighting and know how to take care of a baby right from the start this time, so this time you should have no trouble at all. You know, it's not just the fact that you fall in love with a pet and then lose them, but also that you spent most of the time you had with him trying to make him better, rather than being able to enjoy him. Your son will now appreciate being able to take his new baby out of the tank and just sit and watch TV with him, playing with him, etc., rather than having to let him rest inside his tank all the time, etc.
As far as the BSFL go, DO NOT PUT THEM IN THE FRIDGE, THEY WILL DIE!!!!! They aren't like mealworms or wax worms that just go dormant in the Fridge and then wake-up once you take them out, the BSFL can't be at the low of a temperature, they just die!!!
Here are some BSFL tips to help you out: First of all, always feed the darkest-colored BSFL worms first, as they are the closest to turning, and they also contain the highest Calcium content. Secondly, if you have a place in your house that is cooler than the rest of the house, like a basement or a garage, that's where you should keep them. My house is a "Split-Level" house with 3 furnished, living floors, and I have a garage built-into the house with a door that opens into the basement. My basement level/garage is only used for my workshop (I repair and restore guitars and also used to build custom reptile enclosures and decor), and I keep the heat low down there and just throw some wood on the wood-stove if I'm going to be working down there, it's probably around 50 degrees or so during the winter, same in the summer, it's really cool, so that's where I keep the BSFL. Even if it gets down into the 40's they'll be ok, but below 45 degrees they'll die. I have a 20-gallon long aquarium down there in a closet that I keep them in, and the cold temperature does make them dormant, so I bring down a small container with me when I go to feed my dragons, I just scoop up the amount I need for that feeding, being sure to get the darkest-colored ones, and then I just bring them up in the small container. Then I run them under luke-warm water for a minute or so to wake them up and get them moving around (careful not to drown them, lol), then I dust them and feed them. They say doing this will give you about a month, but I actually get about 2 months out of them doing it this way, keeping them just cold enough that they become dormant but not cold enough to kill them, and then by always feeding the darkest-colored ones first.
I currently have 4 dragons now, I just adopted a rescue guy that was dumped out in the snow, and I adopted another rescue guy with severe MBD about 8 months or so ago from his original family, but I had my first dragon for almost 13 years alone, just him, and he ate only BSFL from 1 month old when I got him until he was about 10 months old, when I started giving him 1-2 Superworms along with his BSFL. And almost a year after he died I got my current female at 1 month old, she's now a year and 2 months, but I had only her for about 7 or 8 months until I got my little boy at a month old. So during the times when I had only one dragon that was about a month old and around 5-6" long when I brought them home, I would order 500 size Large BSFL a month (you should always order size Large, even for a tiny, month-old baby, as they are entirely soft-bodied and they can handle them just fine, no need to waste money on size small or medium). Now it's going to depend on how much fresh salad the baby you get eats as to how many large BSFL he's going to eat per day, but 500 a month should do you, at least order 500 and then see how they're going, then you can always tweak that number. My very first dragon ate a lot of fresh salad every single day, right from day one at a month old, so naturally he ate less live BSFL, although you certainly do not want to end-up replacing a young dragon's live insect protein with greens. For just that reason, if I have a baby dragon who loves fresh salad and eats a lot of it, I never, ever put their fresh salad in their enclosures until after they have their first daily live insect feeding session. I do 3 live insect feeding sessions per day up until 8 months old, then I scale it back to 2 live insect feeding sessions, then they tend to scale it back themselves to only 1 live insect feeding session per day when they are between a year old and a year and a half years old. Just remember that they do most all of their growth and development during their first year of life (they continue to grow up until about 2 years old, when they are officially considered to be "adults"), so that's why from the time they hatch until they are a year old they need a ton of live insect protein every single day. My female hated her fresh salad, every day i made her a fresh salad, she would devour her first live insect feeding, then I'd put her fresh salad in, and she'd either totally ignore it and not go anywhere near it, or she would throw it all over her enclosure, lol, but she rarely ate any greens or veggies, she didn't even like the occasional piece of fruit. All she wanted was her bugs! Then a few months ago when she was around 11 months old, she started to totally refuse her second live insect feeding session, and I naturally started to freak-out that something was wrong. She would devour her morning live insect feeding, but that was it. It took me a day or two to realize that she had started eating her entire fresh salad both these days, lol. So i started feeding her the morning live feeding session of 1 large Superworm and then as many large BSFL as she wanted, and then I made her a large, fresh salad that was double the size that they used to be, and sure enough it would be totally gone. So they tend to make this change themselves and you just have to go with the flow.
I don't know how soon you are thinking about getting another baby, but like I said, if you have a cooler part of your house like a basement, garage, attic, etc. that isn't as cold as the fridge that you can put the BSFL in, they'll survive for about a month that way, assuming that you're not removing the darkest colored ones because you're not feeding a dragon. I actually just bought a 55 liter plastic tub with a latching top for $12 at Walmart to keep them in, so I can move them around easily. i use either Oat Bran or just regular old Oatmeal, like the "Steel Cut" Oats in the canister, as their bedding. If you can find Oat Bran they seem to really love it. Then every day I throw in a handful of the same fresh greens and veggies that I make the dragon's salads out of into the BSFL's container, along with a few pieces of fresh, peeled apple slices or potato slices in a pinch, this is for their
hydration/moisture. I change-out the peeled apple slices once a week, and make sure I throw in some fresh greens/veggies every morning, this way they Gut-Load themselves, which works great to get the fresh greens/veggies into your baby, especially if you get a baby that won't touch their salad, as most of them won't.
Again I'm sorry you guys had to go through this the way that you did, I know you're all the more educated and prepared because of it, and whatever baby beardie you get will be very lucky to end-up in your family, but it's a rough way to get there. If you need anything or ever have any questions at all, please don't every hesitate to post on the forum or to send PM's to any of us any time.