I'm sorry, I think I may have misunderstood you... is there currently no gradient? As in, the whole enclosure is 90*F? If he does not have a cooler side of the enclosure to retreat to, overheating could cause aggression.
Boas are generally aggressive feeders, and will become obese if offered unlimited food. I'm not convinced the problem here is feeding. How often do you feed him? When was the last time he ate? Cage aggression (confusing approaching hands in the cage for food; cage aggression has nothing to do with how much or how often you feed, it simply has to do with feeding response) is fairly common in boas, and can develop with age. The fact that he settles down when you take him out of the enclosure leads me to believe that this is cage aggression; as soon as he realizes that you aren't food, he goes back to being docile.