Protect this hand?

Newbie here; I've been reading SSHE. I don't know if this was an appropriate situation where I would want to "protect my hand" by raising. Also, once I did (and got Villain heads up) I didn't know how to behave on the turn and river. I'm sure this is probably a pretty elementary situation; sorry if it's not very interesting. Any thoughts would be appreciated...

BisonBison didn't seem to work w/ this site's hand history, so I tried to do it by hand...

Texas Hold'em $0.15-$0.30
Hero is BB with 8[img]/images/graemlins/diamond.gif[/img], 8[img]/images/graemlins/spade.gif[/img], Villain is in MP3, MP1 payed a forced bet.
Reads: EP3 and MP2 are both very loose passive. No real read on Villain because he just arrived at the table a few hands ago.

Pre-flop
4 players call (including the forced bet and the loose-passive guys I mentioned), Villain raises, 2 folds, SB calls, Hero calls, everyone else calls.

I called here thinking the odds are big enough to try to flop a set, especially since the loose-passive guys are likely to call for one more bet.

Flop: (12 SB) 5[img]/images/graemlins/diamond.gif[/img],5[img]/images/graemlins/spade.gif[/img],4[img]/images/graemlins/diamond.gif[/img]
SB checks, Hero checks, 4 more checks, Villain bets, SB folds, Hero raises, everyone else folds, Villain calls.

So I flopped an overpair, but it is pretty weak since any card higher than an 8 could make someone a better pair, and there is also a flush draw. I figure Villain probably has 2 overcards or a reasonably high pocket pair. I may have the best hand right now if he has AK or something, but probably not.

Going on stuff in SSHE, I figure I would try to protect my hand by checking to him and trying to raise to make everyone face 2 bets, but I was a little worried that the two very loose-passive players in between may have called anyway. They ended up folding. Is this hand worth protecting, or should I have just folded?

Turn: (8 BB) 3[img]/images/graemlins/club.gif[/img]
Hero bets, Villain calls.

I have no idea how to play the turn here. I decided to bet because he only has to fold a small percentage of the time here for it to be worth it. Maybe he'd be afraid of a straight or trip 5's.

River (10BB) 7[img]/images/graemlins/spade.gif[/img]
Hero checks, Villain checks.

Again, not really sure what do here. Maybe I should've bet again in case he would fold, but I figured because he called the turn that he was likely to call. If Villain had bet here, I would have called because I would've been getting 11 to 1---would that have been correct?