Well I've never rehabbed one but I do own three. If you can keep his temps and humidity correct, which shouldn't be a problem for you since you have experience with another BRB, he should bounce back just fine given that his appetite hasn't been affected by his ordeal.

As you suspected boas do have slower metabolisms than many other snakes so you have to be careful about overfeeding. I've been told the prey should be the same size as or slightly smaller than the widest part of the snake. Your boy didn't get into this state overnight, so it'll take a while for him to put the weight back on.