Kt in 3bettet pot in big trouble

[recallme]

Hero has KTo, Villain is a solid 24/18 player. It was our 1st orbit today and i wanted to show him that he can`t steal my blinds that easy.

4handed 1600 effective

UTG raises to 80, folded to me in BB and i make it 270, he calls

Flop AT6r
checked through

Turn 3
checked through

River K
I bet 400 and he shoves for 900 more

I planed to c/c one streat and fold to further action on turn and river. What you do now?

Is this 4handed in a 3bettet pot still a fold?