ok i am going to avoid all drama here and hope to help the OP. although i am new to this board, i am known on another for my advice, so i will try to help here.
aaron, sometimes the change in environment can cause issues with eating. you said you purchased the gecko from Petco, and then it was at your parent's house for a few days. that is a lot of trauma for a little guy like that, so it may just still be adjusting. now, because he is so little, not eating for that period of time could be a problem. i would keep trying to feed him the mealworms and crickets, but a vet visit for at least a fecal exam is in order. ask the vet for an acid fast fecal stain, as it can pick up more issues than just a regular fecal. you may also want to ask for some carnivorous critical care and ask the proper way to force feed if he does not eat soon.
i would suggest keeping the humid hide, and checking your temps. the container you have him in is rather small, and i am having difficulty figuring out how you are getting any sort of a temp gradient, especially using heat lamps. i myself use lamps and no uths with great success, but had a hard enough time getting the correct gradient in a 28qt sterilite container. i use 25 watt bulbs and get the right temps, a 75 watt on that small container is either only giving him one solid temp all the way across, or maybe the thermometer you are using is not reading correctly? what type of thermometer are you using? those sticky ones have been known to be off by 20 degrees or more, so you might want to invest in a good digital with a probe or a temp gun if you have not already.
i also agree that getting him a "buddy" was not a good idea, especially since he is not doing well, and not in that small container. being so little, any size difference in him and his cagemate can cause lots of stress, as the bigger one may very well being showing some dominant behavior, causing the little guy not to eat. separate them as soon as you can. also, the other risk is with them being so young, they are difficult if not impossible to sex, and you could end up with 2 males, which can be deadly to one or both. i would suggest maybe getting at least 10 gallon cages for each (i prefer 20 longs or 28qt sterilites myself). you should also get the new one fecal tested since he has the potential to be exposed to anything the little one may have.
keep us updated on his progress, as he looks to be a beautiful little one with lots of potential as he grows!