I think I struggle to fold in either situation... the first scenario, being a live home game, is obviously much more dependant on how well you know each other"s game.
In the SnG, certainly at the lower levels (upto say $20), with half the field already having limped in, I think you need a bigger PF re-raise. 150 chips just doesn"t look like a large enough chunk out of 1500 to get all the dross out of the hand, especially if one the EP"s calls... it"s likely they"ll all come along!
You need to make it 600-800... let them know they are gonna be risking their whole stack! In fact just pushing PF, with all those limpers, is probably a better move, the guy with 99 will call often enough to make it profitable.