Fold the river. I can't think of a worse river card.

My gut says there's no way 2-pair wins this pot. We can maybe discount the flush, since Villain has kept firing, and your note says he called when chasing. However, there's a 4 straight on the board; it's about the most dangerous possible board for your hand. Villain has fired 3 barrels, which is almost never a bluff at micros. Hero's hand is beat by any Ax or 9x PLUS all the "coolers" where Villain has made kings up.

Shoving the turn is probably my line, though. Hero had top 2 plus FD on the turn.