WCOOP LHE double-shootout -- tourney theory question

[M.B.E.]

The final table of this double-shootout, there are two winners who each get a $215 seat. Everyone else at the final table gets back their $15 entry fee.

Now we are down to three players: I am in first with 4240, the guy on my right is close behind with 4205, and the guy on my left has only 555. So if he busts out, the tourney is over.

By the way, this is limit holdem. The stakes are currently 150/300.

I limp on the button (150) with pocket sevens. SB (short stack) completes. BB checks.

Flop is J-6-4 rainbow. SB checks, BB bets, I call, and now the SB checkraises to 300. This leaves him with only 105 chips. Now the BB threebets. By the way, I should mention that the BB is a terrible player, a LAG-bordering-on-maniac. He typically will bet or raise with any pair, any decent draw, and sometimes overcards. Maybe he forgot that there are two winners of this tournament (so it doesn't help him to push me out).

So, it's 300 for me to call. Of course SB will call his last chips, and from the way he played the hand, it seems he has my sevens beat. The BB, it appears, is going to bet the turn and the river regardless of whether he can beat pocket sevens.

I folded here, but a friend watching me play suggested I should have called, because the only outcome that would be terrible for me is if the SB wins the hand and the BB also beats me. Anything other than that and either the tournament ends (with me as winner) or it continues (with me as chip leader).

What are your thoughts?