Raise/Call/Fold?

[flippetyflop]

I'm playing a live MTT which started off with 64 runners. It's a 1500 double chance tourny with 1500 and the option to get your other 1500 at any time in the first hour. The blinds starting at 25/25 going up every 20 minutes. I am a bit confused however of what actions I should be taking in the following two hands.

Blinds 25/50

SB 1400
BB 1700
UTG 2000
2nd Guy?
3rd Guy 1600
Hero 2600
4th Guy 1800
CO 1700
Button 1000

Dealt to Hero

AH 10S

UTG who has been playing tight poker so far limps in

P3 who I've cast as a weak player also limps

and i decide to limp with my ace ten.

Flop comes j 4 6 and everyone checks

Turn comes an ace and as it comes I notice the UTG player look directly at me.

Its checked roudn to me and with pot at 500 I bet 400 into it.

UTG calls my 400 and raises 800 more. He has about 400 left. What is my line here?