Losing my nerve with a chip lead?

[cheburashka]

I’m chip leader in a 1.20/45 (it really sucks to have a depleted bankroll), and I’m playing my standard TAG game (22/15/1.8). I’ve been blessed with good cards; on the first hand I flopped a well-concealed straight at the same time villain flopped a set, and it’s been all good news since.

Villain is a bit loose and very passive (28/2/0.3), but I haven’t seen him do anything ridiculous.

Hero (15632 in chips)
MP (6250 in chips)
CO (13257 in chips)
BU (9873 in chips)
SB (11055 in chips)
BB (11433 in chips)

Blinds 400/800/50; Hero is UTG with 7 [img]/images/graemlins/diamond.gif[/img] 7 [img]/images/graemlins/spade.gif[/img]

Hero calls 800, three folds, BU calls 800, SB folds, BB checks.

Flop (3100) J [img]/images/graemlins/club.gif[/img] J [img]/images/graemlins/spade.gif[/img] 9 [img]/images/graemlins/diamond.gif[/img]

BB checks, Hero bets 2400, BU folds, BB raises 2400 to 4800, Hero???

Checking the BB, villain could have pretty much anything here—lucky 9 or J, QT, or nothing.

I don’t want to jeopardize what has been my best tourney in quite some time with a pair and three overcards. But I don’t want to get in the business of protecting leads and passing up positive EV situations. So raise, call or fold?

Also, in 9-handed play I am always playing 77 for set value from EP (I’m going to need a lot more confidence in my game to do otherwise, so don’t even try to get me raising UTG). However, is this still OK six-handed, or should I really have raised here?