Then I would stick in a call, since you would be risking much less, and he would be on a wider range.
I disagree. Unless BB is a clueless fish, this is never AJ, AT or KQ. At best it could be another AQ, but more commonly its AK or a big pocket pair like TT+.
Are ranges really that loose, when there are only 13 players left? I have played a lot of MTTs on PokerStars, and its certainly not my experience, that a lot of wild gamblers are left at this stage of a $5.5 MTT. Usually they tend to bust must earlier. Are you using a tracker/HUD, so that you have actual information about the other players at your table? If not that might be a good investment, if you play regularly.
Yes this is true, but SB is representing a much narrower range, and since he is all-in, BB have no fold equity, so he cant bluff. The risk/reward is also unfavourable for BB, since he has to risk his entire stack against you to potentially play a flip with SB for his 7BB. And especially with ICM this mean, there is a ton of incentive for BB to pass on this one and let you try to bust SB.
Its also kind of a tell, that he only called, even though this committed him to the pot. Its like saying "please give me action", and alarm bells should be going off in your head. Realistically his range might be as narrow as QQ+ or even KK+, if we go with that read. Its a bit like, when a solid regular suddenly limp UTG with a 10BB stack. Not because he is trying to see a cheap flop, but because he has pocket aces and want to induce action.