I think the odds that this is an elaborate prank is pretty slim. Chances are you started to be nice to him and he developed a crush. I think your instincts are correct that he might become a jerk again once the big early crush feelings wear off.
The bottom line is that you know he’s capable of making you feel bad about yourself. It’s good that you managed to bury the hatchet with him but you don’t owe him anything outside of that.