HU Play

[TruFloridaGator]

$10+1
Blinds are 150/300

Hero is SB (T9000)
Villian is BB (T4500) - This guy has called everyone of my raises HU(of about 3x+ blinds) with any conceivable hand, every hand is within is limping & raise calling range.

Hero is dealt Ac9h

Preflop:
Hero raises to 900, Villian calls.

Flop(1800) - 7h6h3s
I bet out 1200 & then he re-raised AI to 3600.

Is a call here awful or, or is there a better move for me to make? My HU struggles continue. I'm winning HU still but I feel I am making to many mistakes along the way.