Congrats on the new guy. seems like its a male, im 99% sure based on what i saw on your other post. I would say about 3 or 3½ months old at least, kinda hard to tell, some grow faster than others.
Feeders:
Be careful with the crickets free ranging, they can pick at your cham at night and injure his scales. I will add some dubias to his diet too.
Supplements:
Your supplements seem fine, for multivitamin i use zoomed reptivite without D3 and i would alternate with vit. d3 every weekend. Lets say you choose Saturday to give the extra supplement, so one Saturday do D3 the other Saturday multivitamin and so on. And all the other days just regular calcium with no d3.
Cage: you'll need at least a 24"x24"x48" cage.
Basking temps as long as they dont exceed 85 you should be fine. Make sure he doesn't get burnt when he screen climbs, so have the adequate height between basking light and cage top.
Everything else seems good so far. Also, i know you already said you're getting the linear uvb, but that's really crucial for them. I would get that asap.
Welcome and good luck!