.05/.10 NLHE 6-MAX

Button (HERO) : $12.96
SB: $10.39
BB: $1.25

Hold to HERO on Button with As9c, Raise to .30
Both blinds Call.

Flop: Ac 4c Qh

SB Checks, BB Checks, HERO bets .50
Both Blinds Call.

Turn: 9d

SB Checks, BB Checks, HERO bets $2.00
SB Raises to $6, BB Calls All-in for his remaining $.45

I thought this was an interesting spot, given the action I couldn't think of that many combos of value hands he could have that beat me (couple combos of 44, one of 99, and a couple of A9 that I'm chopping with). I had him weighted pretty heavily towards flush/straight/combo draws. BB also getting it in might mean the BB has the more made hand and SB is trying to iso with strong draw and pick up possibly 20 dead bb?... To me a raise like that screams "I have AQ or better" but how often can we ever our opponent AQ, AA, or even 99 in this situation?

I decided to flat the $6 and decide what to do on the River, if I don't fill up just try to get to showdown. I'm not eager to get it in here, but I thought my hand was too strong to fold. I figured there wasn't much reason for SB to continue to bluff if he was on a draw and missed since he has to show down against BB anyways, and when as the preflop raiser I bet flop and call raise on turn I still have all the top value hands in my range so I thought there was a good chance of checking down river.

River 3c

HERO Checks.
SB Checks.

Showdown:
SB has 4s 4d
BB has Qc 2c

Curious as to what others think of this hand, and my thought process. He happened to have the one value hand I thought he could have had in this spot, but given all of the draws or overplayed AJ,AT,etc he could have had I feel ok about my turn call. Anyone think this is a clear fold on the turn? Thanks!