[bbartlog]

I don't like the turn bet. It's small enough that someone may call you with just the nut low draw, but big enough that someone who has the ace-high flush can comfortably flat call knowing that they'll still be able to get it all in on the river. In general I think that if you had been thinking ahead to the next street(s) and figuring that you'd be willing to get it all in, you should have been pushing a little harder to begin with just to get some fold equity. So pot-raise flop (or fold), check turn or pot it if you're going to bet at all. I think I favor the flop fold and the turn check though.
As for button flat-calling on river, I don't think you can read weakness from that. I would expect him to put CO on the nut low (just as you did), and if he has the A-high flush but not the nut low then most of his profit would be from getting you to call; it would be pointless for him to do anything (like raising) that would make it more likely for him to get HU with the CO for a 50/50 split.