nut flush draw, turn & river questions

IMHO, you made all the right decisions. I'd bet the river here, it is likely you have the best hand. I put SB on a Qx or JT, and MP1 on an OESD and flush draw.

If you are raised by SB, and MP1 folds, call for 1 more bet. If MP1 cold calls SB's raise, throw the hand away. 1 of them is likely to have at least 2-pair in this situation.