ATs a very confusing hand

UTG is unkown, Button is very loose pre-flop and pretty average post-flop. Big Blind is classic LPP but is short-stacked.

Any comments are appreciated, but I've got specific questions too:

1. Anyone 3-bet this pre-flop?
2. Would a check-raise on the flop be better than the donk?
3. Does anyone drop this when it's 2 back to them on the flop?
4. Can I call this river?

PokerStars 3/6 Hold'em (5 handed) FTR converter on zerodivide.cx

Preflop: Hero is SB with T[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">UTG raises</font>, <font color="#666666">1 fold</font>, Button calls, Hero calls, BB calls.

Flop: (8 SB) 5[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">BB raises</font>, <font color="#CC3333">UTG 3-bets</font>, Button calls, Hero calls, BB calls $0.50 (All-In).

Turn: (8.58 BB) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players, 1 all-in)</font>
Hero checks, UTG checks, Button checks.

River: (8.58 BB) J[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players, 1 all-in)</font>
Hero checks, <font color="#CC3333">UTG bets</font>, <font color="#CC3333">Button raises</font>, Hero??