The reason you prob shouldn't fold now I think is the pot odds you've created for yourself. Even if you are behind the range he's shoving you still likely have odds to call.
Actually, thinking about the math ....our decision to call villains iso reshove doesn't involve any extra money for pot odds, because the antes and blinds are being raced for 3ways . so since we are behind his range we need to make up the ev in the 3 way race which I don't think we do. That would make flat/folding best ...but I don't know if all i just said is correct.