3 bet on the river with the 2nd nut flush

[Malificent]

This hand is NL50 at a B2B site, so apologies in advance for the not quite as clean hand history. No real reads on the villain except that he's willing to be aggressive when necessary - didn't see him as LAG and the few hands that I've seen him showdown were legit.

I don't like my preflop limp (not sure what the hell I was doing there) so feel free to rail against it. As played, I'm interested in whether my raise on the river is smart and what I should be doing when I get 3 bet.

Players(max 8):
1 (EUR 39.00 in seat 1)
2 (EUR 34.30 in seat 2)
3 (EUR 25.00 in seat 3)
4 (EUR 38.30 in seat 4)
Villain (EUR 50.00 in seat 5)
6 (EUR 50.60 in seat 6)
Hero (EUR 102.15 in seat 7)
8 (EUR 79.27 in seat 8)

Dealer: Player 3
Small Blind: Player 4 (0.25)
Big Blind: Villain (0.50)

Hero was dealt: 8d - Kd

1 fold, Hero Call (0.50), 2 folds, Player 4 Call (0.25), Villain Check

Flop 3c - 4d - 7d

Player 4 Check
Villain Bet (0.50)
Hero Call (0.50)
Player 4 Fold

Turn 3c - 4d - 7d - 6h

Villain Bet (1.00)
Hero Call (1.00)

River 3c - 4d - 7d - 6h - 9d

Villain Bet (4.50)
Hero Raise (12.00)
Villain Raise (35.00)
Hero ???