The difference between 6th and 7th doesn't really appear to be enough to warrant folding 55, at least imo. The difference between the higher payouts (namely first) and 6th is plenty enough for me to think shoving is the best move.
OP didn't list all stack sizes but I'm guessing that unless the structure/play was horrible that he was well well out of contention for a big cash. If it is a kamikaze blind schedule and *everyone* has less than 5 BB then yeah I'd say go for it and hope to get lucky. I'm just skeptical that that was the case here. Dunno though without more info. As for the jump between 6th and 7th, it is one and a half tourney buy-ins so I don't think it's anything to sneeze at when balancing the benefits of trying to back into 6th.
Either way it's a gamble because if short stack gets lucky and doubles up then it is the OP who is stuck trying to avoid being blinded out but assuming the luck factors equal out I'd take my chances trying to move up a spot since the other player has a shorter stack and is about to get hit by the blinds.