Did I read correctly that you attempted to feed it the day you got it? If so, it might have associated the food item with the stress of being moved from familiar surroundings into a big, new world where nothing smells quite the same and every part of the place is a potentially dangerous unknown. I gave Saga a full week to get adjusted to her new home without doing anything more than changing the water from time to time before the first attempted feeding. She was flighty and snappy the first time I got her out, too, but she ate when I offered food....
You mention ambient air temp. Ambient air temp is usually lower than the temp at the glass/substrate level, often a
lot lower, in my experience. Corns don't really care what the ambient air temp is, as long as it's above 60 or so; they need belly heat. You really need a digital thermometer with a probe or a temp gun to know what your corn is
really experiencing. In my experience with two different thermostats (a $20 Zoo Med and a $45 BAH), the Zoo Med always needed to be turned way up to 95 to achieve a temp of 80-85, and the BAH needs to be set closer 75 to get the same results. I don't trust the accuracy of those things by themselves anymore. >_< It seems likely to me that your corn's temps might be a bit too high, given his behavior and the ambient air temp.
Since I come from a cool, humid climate, however, my experience with ambient air temp might not match up with yours. :P
Also, did you find out
what the Petco people were feeding him? The Petcos and Petsmarts up here all feed only one, tiny pinky head every four to seven days. If your corn has been eating something that small, the full-size pink might seem too big. If you haven't already, I'd say to try and get ahold of the smallest-possible pinks, newborn or day-old if possible. Most Petsmarts sell them. The smaller size might help the baby realize he can, in fact eat the mouse put in front of him. XD
When Saga didn't want to eat, I used two pairs of tweezers to break the belly skin of a really hot pink, then left it with her in a cupboard over night. Worked like a charm.
Saga was quite the rattler when she was was a wee hatchling! Turns out all snakes have the muscles for it, and snakes whose ranges overlap those of rattlesnakes seem to have picked up the habit! XD Interestingly enough, rattlesnakes are starting to kick the rattling habit lately. Apparently, the rattling behavior has outlived its usefulness, since more rattlesnakes are killed by humans than by any other predator, and what was originally an effective warning/self-defense system only backfires when the snake rattles at humans. While a coyote or a mountain lion will usually leave a rattler alone, humans will locate and kill it.