[donger]

Don't forget the little straight. Anybody with 56 has an OESD and isn't going anywhere on the flop. BB's play is consistent with a hand like that.

Edit: I would raise the river and call a 3bet.

Preflop, I would still just raise. If BTN really is on tilt, he might be more likely to three-bet your raise (and try to isolate) than to raise your limp (and know the blinds are probably coming along)..