Tough river decision on 4-flush board

Limper is a fish, and villain is an aggressive reg. I believe KQo is ahead of his isolating range, and I have position anyways to justify pf call. I also feel that turn and rivers are pretty much the perfect cards for him to barrel bluff. Although I feel like he either has an As or air by the river. I dont see why he would keep betting AK no spades, or AA no spades. So it polarizes his range towards As (maybe Js) and air.

Do you guys agree with my thought process? Does that make river a call...What about the turn?

Cryptologic
No Limit Holdem Ring game
Blinds: $2/$5
5 players
Converter
Seat 1: SB ($683.30 in chips)
Seat 2: HERO ($1517.35 in chips)
Seat 3: Blu_Blood ($816 in chips)
Seat 4: Zooom88 ($394 in chips)
Seat 5: agfagf ($187.90 in chips)
Seat 6: RiverDunk ($167.70 in chips)
Pre-flop: (5 players) Hero is BB with :qh: :kc:
UTG folds, CO calls, Button folds, SB raises to $30, Hero calls, CO folds.

Flop: :7c: :3s: :qs: ($65, 2 players)
SB bets $49, Hero calls.

Turn: :ks: ($163, 2 players)
SB bets $119, Hero calls.

River: :8s: ($401, 2 players)
SB bets $300, Hero???

Results:

given that you called two streets and the 4th flush card comes on river i just dont really see this being a bluff that often.

[]tough river decision

[x] aggressive game where people run multi-street bluffs

[x] should have raised the turn

yeah

[x] stop using these stupid boxes everyone.