Well I'm not a 5/10 player (keep that in mind) but that's never stopped me from throwing my .02 out there

. If the SB is a LAG he possibly could be 3 betting here with anything, also I think your image can come into play here especially if you've been trying to steal a lot.
Anyway, looking at the action on the flop he apparently likes that flop so some hands that seem to make sense we can put him on are (AT, KT, TT, 88, maybe 44 as the big ones possibly an overpair as well)
Turn he isn't slowing down because he led out, but looks like he can be concerned about the flush here or was possibly trying a semi bluff representing one himself.
River card pairing the board is where I'd be concerned.... Going off the action:
He knows you've 3 bet his CR on the flop and raised his bet again on the turn. Now
he's leading out again after getting raised all the way on a board that has all the ingredients for a big hand out there. My thoughts are he's not worried about getting raised again here.
Personally I'm prorbably just calling here....we've done everything we can to get him off this hand by raising him the whole way. Now on the river he's leading into us again (knowing we've raised him every time), so he hasn't given up on his hand and if he had anything that couldn't beat at least a flush I would think he'd check the river.
Has the board not paired and he led out again I'm raising and definately betting if he checks.