Yeah, Superhuman difficulty isn't really that much fun. It's all right if the game feels too easy otherwise, but there's no need to use it otherwise. Not like it can't be played, but it's not any better than, say, Blackbeard. Besides, it always uses max enemies, so you always know how many are left!
If you want to change difficulty, find this line in the save:
difficulty: 4
Change the number to something lower, like 2... Save, done.