J2 and a tough river decision

Or maybe I went wrong before the river. This is on the party 5/10 game, HH is from memory but I'm pretty sure it's correct.

SB is a typical 44/10/1 after 20 hands or so, CO is a 44/0/.6 after 100 hands who goes to showdown 45 % of the time.

Hero has J2o in the BB. CO limps, Button limps, SB limps and I check.
Flop (4 SB) : J [img]/images/graemlins/heart.gif[/img] 7 [img]/images/graemlins/heart.gif[/img] 4 [img]/images/graemlins/spade.gif[/img] SB bets, I raise, CO calls, Button folds, SB 3-bets [img]/images/graemlins/confused.gif[/img] and we both call.

Turn (6.5 BB) T [img]/images/graemlins/diamond.gif[/img] SB bets, hero calls (?), CO calls.

River (9.5 BB) K [img]/images/graemlins/club.gif[/img] SB bets, hero ?

I really really don't want to overcall the river with top pair no kicker, and I'm worried that CO's call down range includes a king at least 1/3 of the time here. I think I should have raised the turn, but if I get 3-bet can I really fold to the chance he has a lower two pair or overpair I'm drawing live against?

Comments welcome on all streets.