Opp is a total LAgg donkey - stats 64/11/1.8 over 70 hands. He had stacked off with TPNK against my overpair previously.

What to do here after opp effectively pushes the flop? Unless he has a set or two pair I figure I'm at least 50/50 against whatever he is pulling this with, I have to call, right?

PokerStars No-Limit Hold'em, $0.25 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG+1 ($48.45)
MP1 ($20.95)
MP2 ($29.10)
MP3 ($11.70)
CO ($22.65)
Hero ($52.20)
SB ($24.75)
BB ($39.30)
UTG ($8.05)

Preflop: Hero is Button with 4, 6. MP3 posts a blind of $0.35.
4 folds, MP3 (poster) checks, 1 fold, Hero calls $0.25, 1 fold, BB checks.

Flop: ($0.95) 7, 9, 4 (3 players)
BB checks, MP3 bets $0.75, Hero raises to $2.5, BB folds, MP3 raises to $10.5, Hero ????