hi there, i think the biggest issue is over supplementation. jacksons are a little more sensitive to over supplementation than some of the other species. i would reduce the t-rex icb to once every month, (sparingly), until he looks better, then after that, (sparingly) once every 2-3 weeks should be plenty.
t-rex icb is considered an "all in one supplementation, containing both preformed vitaminA (vitaminA acetate @480,00 iu/kg,) and proformed vitaminA (in the form of beta carotene@1000 mg/kg) calcium plus icb is actually a fairly complete and well balanced product, its (imo), just too concentrated for daily use on jacksons and most chameleons. dont be fooled into thinking it is formulated specifically for chameleons, yes i know there is a picture of a chameleon on the label and i know they call it chameleon calcium plus icb, but thats just for marketing purposes the exact same product is also marketed as Bearded Dragon ICB, Tree Frog ICB)
i think it is still a viable product when used in moderation where chameleons (especially jacksons) are concerned. since it is an all in one multivite, if it is to be your product of choice, then no other vitamin/supplementation should be given with it, EXCEPT, it might be good to (sparingly) give plain calcium 1x a week as well.
as far as caging, jacksons can do well in appropriate glass caging, but glass caging presents several issues, which i think are better addressed by more experienced keepers. as well , most reasonably priced, commercially available glass cages ( like exo-terras ) are imo, too small for an adult jackson, he should have at least an 18"x24"x36" cage at minimum, and preferably a 24"x24"x48". if you can afford to make the switch i think he would do much better in a regular screened cham cage of those dimensions.
temps cannot be acurrately monitored from a single location. temps should be measured in at least 2 locations throughout the cage, at least until your cage is dialed in. it wouldnt hurt to monitor your humidity also. you can get a digital thermometer/hygrometer (also measures humidity ) zilla makes a decent one for under $20, you can get just digital therms for less than $10.
as far as lighting, imo a 10.0 cfl is considered a desert bulb and not well suited to jacksons, it should be replaced with a 5.0 preferably a linear, (not cfl). probably a good idea to get rid of the infra red and replace it with a regular incandescent house bulb of 15-40watts. jacksons, dont need or desire any heat at night, in fact a 12-15* drop in nightime temps is desireable.
jacksons do best in cages that are well planted with live lush plants.
as far as diet, like most chams, a jacksons will not do well long term on just a never ending stream of petstore crickets, regardless of how they are dusted. the subject of both dieting and supplementation are far too extensive to address in a single post but for many reasons, a jacksons will need a wide variety of feeders, other than crickets, and if you are not prepared to start raising bugs, you can get a fairly good variety of non cricket feeders online (blue bottle flies, silkworms, hornworms etc)
vids on how to raise most common feeders are available on you tube.
heres a short recap; discontinue the icb at least until there is some improvement. replace the 10.0 cfl with a 5.0 preferably linear, replace the 50 watt infra red with an incandescent of 40 watts max. get him some feeders other than crickets (blue bottle flies are good for breaking hunger strikes) and begin studying supplementation issues and husbandry issues in general. until you get a better understanding of supplemental issues, you may want to use a commercially available gutload or there are some members here on the forum that make and sell theirs. a good gut load has at least a couple dozen ingredients. jacksons do best when their basking spot is above eye level, and i would be careful about putting an all glass cage where it is exposed to sunlight. he should also have a dripper and water available during all daylight hrs. jmo