Hello Amber,
Well, it is somewhat hard to tell how old they are. You can kind of tell by the way that they shed, as babies have softer skin & tend to shed in whole body phases. Whereas adults, they have a little tougher skin & shed more in patches instead. Also, the heads start to mature more & widen too as they get older. The bulges on top of their head & above their eyes change in shape as well.
That is hilarious he went chasing after a bug! I think the fastest bearded dragon was clocked at 100mph so watch out! LOL No, just kidding, but, they are very fast. Do you have hawks or large predatory birds in your area? If so, watch for them because they will dive at them. He will take off for cover if he sees one too.
Bell peppers are fine for them. No problem, you can use red or green, or the other colors too. It is challenging to get them to eat their greens!
That is fine, the light can wait since he is getting sunlight daily & calcium he will be ok until then.
It sounds like he is doing awesome though, great job with him.
Tracie