Hi and welcome to the forum. That's great that you're trying to help this sick beardie. Glad to hear that you're been keeping him well
hydrated. I also would suggest you not feed the mealworms because due to their chitin shell, it makes it hard for them to digest especially since young beardies have a kink in their digestive tract. Pinkies are also hard for them to digest. Better choices would be crickets (no larger than the space between his eyes), hornworms, silkworms, phoenix worms, butterworms or roaches like dubias. He's really not big enough for supers yet as they can be hard to digest unless your beardie is closer to 16" long. I would go easy on the protein right now since he had such a poor diet previously. Here's a site that shows the best greens to feed:
http://www.beautifuldragons.503xtreme.com/Nutrition.html
You really should invest in either a temperature gun or a digital thermometer with a probe end right away. If the temps aren't accurate, they won't do well & it will affect their appetite, pooping, activity & overall health.
If you have an 8.0 bulb, it must be a Repti-Glo rather than a Repti-Sun. It is a strip fluorescent bulb, rather than a coil/compact bulb, right? How far away from the UVB is your beardie? Is the bulb new?
As suggested, continue to
bathe him regularly & at least once a day. Would also be a good idea to feed him babyfood slurry of squash, applesauce, garden veggies and chicken. Only put a small amt of chicken with a larger amt of squash or veggies as you don't want to tax his system with too much protein. You could also use some diluted pedialyte and a plastic syringe to drop on his nose for him to lick off.
Please keep us updated & thanks for helping out this little guy.