I wasn’t sure whether the king and pawn ending was going to be winning or not, but before I traded rooks realized that his backward isolated pawn was no worse than my isolated and doubled pawns, so I went in for the rook trades.
He didn’t play the opening and middlegame sharply enough or subtly enough, so I dodged big bullets there, and then he was trading into a seemingly lost ending, so that I was fortunate to bypass a potentially extremely tough middlegame for a simple one.
After the game, I mentioned to him that he could have put his king on a6, then played pawn to a5 and try to stalemate himself, but it wouldn’t have worked because I would have played the pawns the way I did in the game to avoid stalemate.
Also, I thought he might try one last trick with 39.g5 fxg?, 40.h6 gxh, 41.f6, but I was obviously prepared to play 39…h6! (forming a pawn-triangle) or I wouldn’t have wondered my king so far from those pawns. I actually wasn’t planning on taking his a5 pawn either, was just going to push the c-pawn all the way, and then zugzwang him into giving up his f and g pawns, or making him play a pawn to g6 so that my king can eat his f pawn.
Well, I could kibitz this game now and see what Stockfish thinks, but I can also finish annotating it.