3 way 5-5PL hand OOP

[evil_twin]

5-5pl, we are 10 handed. Standard game, no special reads that these guys are idiots, but they may be. I'm not really a regular OH8 player, I just play occasionally for variation.

Hero is SB, dealt 8[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] A[img]/images/graemlins/club.gif[/img] 6[img]/images/graemlins/club.gif[/img]

Preflop : 2 folds, EP calls $5, MP1 ($505) calls, MP+1calls, Hero ($600) checks, BB ($320) checks

Pot is $20, flop 8[img]/images/graemlins/club.gif[/img] 6[img]/images/graemlins/diamond.gif[/img] 10[img]/images/graemlins/heart.gif[/img]

So I've flopped bottom 2 pair with the nut low draw.
Hero bet $20, BB calls, 1 fold, MP calls, MP+1 folds.

Pot $80, Turn 2[img]/images/graemlins/club.gif[/img]

3 pair now plus the nut flush draw. Enough to continue betting out right?
Hero bet $40, BB calls, MP calls

Pot $200, River 2[img]/images/graemlins/heart.gif[/img]

OK so I've rivered an underboat and quite probably have the best high hand.
Hero bets $100, BB calls, CO raises to $300.
My action? Can I consider folding? Insta-call? Comments on all streets welcome.