15/14 is getting close to nitty for a reg, and he played this AA super cautiously (I'm pumping turn for sure expecting AK/KQ/draws to pay me), so I'd consider him very tight for future analysis.
That said, I like your play. If he has the flush he's likely raising river so we're really thinking about how to get the K to pay us off. On level 2, a triple barrel on this river looks like thin value or nuts, not the best bluffing
card. I probably end up betting about 2/3 pot to make him think he's getting a good price. It's tough to find a fold with AA but I would consider his willingness to pay off this big a value bet as a possible leak.