You need to call 15 to a pot of 200. The chance of him just shoving lower flush for last few bucks is greater than 0%. The question is, how often he has Jhigh flush or random brainfart there? Your assumption is that less than 8% of times, I wouldn't be surprised if it was over that 8%.
If we are willing to bet pot for value on the river, the question is would there be more value with smaller sizing? We target lower flush or hero calls, and with smaller sizing he will call more often with those. Of course it opens the door for a bluff, so we have to decided if we bet-call or bet-fold, especially if our chosen sizing is smaller (as then his c-raise bluffs have more leverage).
I wouldn't pot fold here. If we fold to a raise of 15, where do we draw the line? If he raised 1bb more, we would call for sure. So the threshold is somewhere between 1 and 15. What would Ghaleon estimate, what is the chance for him to shove remaining 15 with Jhigh flush?