acclimation
he can easily go a couple of weeks without food, and they are susceptible to hunger strikes during times of stress, so, imo i wouldnt even bother him with food for the first couple of days. instead i think your efforts might be better directed at getting things his cage location, and temp zones dialed in. try to think of any improvements or changes you might want to make and make them all at once. then you can just take him out and let him crawl around on a houseplant or the curtains or something while you make your changes, rather than bothering him everyday for the next week.
bear in mind they are arboreal (tree dwelling) and much more comfortable when their basking spot is at or above eye level.
also good to consider cage location. kids, pets, stereos, tvs, lights that are frequently turned on and off, heat registers, excessive foot traffic in close proximity of the cage, all can be a problem.
all he really needs now is uvb, plenty of water, foliage, and for you to get out of his territory.
im sure in 2 or 3 days he'll be more than ready for food. 5 med feeders 4 or 5 days a week is plenty, its not good to feed captive xanths all they will eat and it would be good if you could get his night temps down to at least 64* without using fans, airco or being in direct proximity to an open window.
i dont know what your intentions for a supp plan are, but imo, might be a good idea to fill out the help form and bounce it off of forum members, if you dont have a supp plan, just list whatever supp brands you have on hand . imo, i wouldnt recommend any supping other than a couple of matcheads of plain cal a week. until you get a balanced plan. he can easily and probably should go several weeks without any multivites, probably a good idea to submit the help form before you give any d3 either.
imo, whether experienced or novice keeper, 85-90% of xanth health problems are caused by poor diet or oversupplementation, they need very little, so imo, if they are getting any at all they arent likely getting under supped, imo, thats an almost non existent scenario. jmo