Alrighty, so there's definately a few things that you will need to change.
I'll go down according to the list.
First off, your baby should be in a minimum of a 40 gallon breeder. Larger is better, though 7 inches is quite small for a 7-8 month old beardie. Are you measuring just his body, or from his snout to the tip of his tail?
The coil reptiglo uvb lights can cause eye problems, and as of now the only UVB bulbs that are found to be safe are the ReptiSUN 10.0, Arcadia 12%, and MVB bulbs, though there are different types of those, so I'd reccomend doing a big of research if you go with that.
The black bulb really shouldn't be used, as we've already discussed above, though you don't need a nightime heat source since your tank doesn't drop below 65.
The dial thermometers can be extremely inacurate, so you'll want to pick up a digital thermometor with a probe, or an infrared temp gun. I am unclear if what you have is a digital one, as I don't know of any dial thermometers with a digital attachement. Regardless, you can get a cheap digital with probe at walmart for like 10 bucks, they work great. The dial ones can be off by up to 20 degrees in either direction.
Your temps should also be higher in the basking area. You'll want to place the probe directly on the basking spot where your dragon hangs out, and you want it to be between 105-110.
You also do not need to purchase a heat rock, as they can cause the same kind of dangers as heat pads. I'm not sure why the girl at the store wouldn't know that, if she knew about the problems of heat pads.
Now- to feeding.
You definately need to be feeding him more. He should be getting at least 2 meals a day, and as many crickets (no bigger than the space between his eyes) as he can eat within 15 minutes or so.
You should also offer him salads daily..Even if he doesn't really seem to be eating them very much, it's good to get into the habbit now.
Mustard greens are good, but they really thrive on variety. Here's a link to an excellent list for feeding.
http://www.beautifuldragons.com/Nutritionframeset.html
Also, I would definately reccomend doing a feeding before you leave in the morning. Just make sure that he has enough time to warm up before you feed him.
You'll need to make sure you're giving him at least 2 hours of basking after a meal before shutting the lights off for the night as well, otherwise they don't digest properly.
As for your calcium, is it the calcium with D3?
You'll also want to purchase a good vitamin supplement. Many people use Reptical. There are also some all in one supplements, which have both calcium and multivitamin together. Repashy Calcium Plus is one of them. If you don't get the all in one, you should do calcium 5x days a week, and vitamin 2x a week.
Also, you really should take the water bowl out of his tank, as it raises the humidity and most of the time they don't drink from it.
You can give him baths 2-3 times a week to keep him
hydrated. They absorb water through their vents, and some of the time they will also have a nice drink while they're in there. Just make sure that the water is lukewarm, like you would for a baby, and comes up to around his shoulders.
If he's freaked out the first time you
bathe him, you can try putting a towl underneth him to give him some traction.
You should also not mist him in his tank, as that too will raise the humidity, which can lead to upper respiratory infections.
If anyone else has anything to add, jump on in.
I know it can seem like alot to take in, but once you get their set ups and feeding scheduals down, then it's all cuddles and fun. For the most part anyways! ^_^