Completing form SB

Hopefully this should be standard stuff but never hurts to check right? It's not too uncommon for me to run into a hand like the following:

Party Poker (6 max, 6 handed) converter

Preflop: Hero is SB with J[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">2 folds</font>, CO calls, <font color="#666666">1 folds</font>, Hero calls, BB checks.

Flop: 4[img]/images/graemlins/spade.gif[/img], 2[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
Hero checks, BB checks, CO bets, Hero ???

CO is 59/14/0.72 over ~70 hands. Was pretty weak and seemed to fairly consistently bet any street somebody else didn't.
BB is 44/6/1.94 over the same. Seemed like a pretty decent player

Now my questions are:

1. I know when facing a raise it's pretty much reraise or fold from the SB but when one opponent from late has limped and the BB is pretty passive preflop is limping the way to go? It's too good to lay down and it seems pretty unlikely the BB is folding to a raise.

2. What if the BB was really tight? What's the worst hand you'd raise here to fold the BB and punish the CO for limping with crap?

3. With an aggressive BB and NO draw this flop is an easy fold unless I'm way off. But what kind of draw is enough to raise the CO on? The 2 overs plus a gutshot? 2 overs plus a gutshot and a bdfd? Better than that? How much lower would the C/R bar be if the BB was really weak?