I am torn about turn bet size.

8 or A of spades gives him the flush and us a boat, and if 1/2 pot is the most we lose when we bet $6 on turn, then maybe small bet isn't so bad. He just barely is getting implied odds (~5:1) unless you are calling $20 or more. $9 on turn makes him make a bigger mistake, but he might fold which is not really good.