looks ok to me. i mean once the board pairs on the river he is only repping 6 combos that beat you. unless he flats pre/donks flop w/76s in which case it's 10. even then, i imagine this would be a call if the very bottom of his range is KQ:

Board: 5c 3c Kd 4s 5s
Dead:

equity win tie pots won pots tied
Hand 0: 45.833% 33.33% 12.50% 8 3.00 { AsKc }
Hand 1: 54.167% 41.67% 12.50% 10 3.00 { 55, 33, AKs, KQs, 76s, 53s, AKo, KQo }