AK hits but faces big push.

[EsandWhizz]

Poker Room skin
Pot Limit Holdem Ring game
Blinds: $0.25/$0.50
5 players
Converter

Stack sizes:
UTG: $221.95
Hero: $85.90
Button: $55
SB: $109.70
BB: $10.90

Pre-flop: (5 players) Hero is CO with :ah :kd
UTG calls, [color=#cc0000]Hero raises to $2.5</font>, Button folds, SB calls, 2 folds.

Flop: :ad :4h :4s ($6, 2 players)
SB checks, [color=#cc0000]Hero bets $4</font>, [color=#cc0000]SB raises to $10</font>, [color=#cc0000]Hero raises to $29</font>, [color=#cc0000]SB raises all-in $97.2[/color

No stats on SB and havnt played any big hands with him or really noticed him much and iv been raising alot of his blinds and hes been folding. He seems to be playing TAG. What in his range could contain a 4? Is this ever a weaker ace? Is this an insta-muck? Is the flop 4 bet ok? Thanks for any replies.