Like someone else mentioned getting him treated is top priority right now. Also the one ficus tree is not good enough but husbandry will go after you’ve taken him
It should be the length of, or a foot longer than, his cage, and it should be 8-9” away from his basking branch (with it over the screen top of course).
Remember to put your branches 9 inches down from the t5 bulbs.
Also change supplement schedule immediately
make sure to get the appropriate size bulbs for your cage size
*edit* I gave you 2 different links for 2 different t5 bulbs. Whichever one you choose to use will do just fine. The reptisun should be replaced every 6 months and the Arcadia 6% bulb replace once a year