To me, it reads like a story that was stretched past its intended end point for some reason? I mean, you can wrap the story up at many places past chapter 79, each giving the work a different flavor.
At the cabin, it would have been a ghost/horror story with MC finally overcoming the impossible. Contracting with him would end the story at pretty much sequel bait. Him giving up his power, walking away or even sealing himself up would have been a start to redemption, as would him actually giving MC power instead of blondie. The confrontation with the villains could have changed it to a thriller, especially if the queen actually found a way to be a threat. It didn't even need to put MC together with him, it could have just ended with him becoming a true protector to what she held dear, even after she passed. But I guess none of those would be this story specifically.
What I feel the weirdest about is that ML isn't really human to me, more like a great old tree-god or some kind of alien species fundamentally incapable of truly grasping romantic love. I do appreciate his strange mind tho, so it was kinda weird to see it end the way it did. Well, at least the first 80-ish chapters were fire, and the ending wasn't all that bad overall.
I can follow a story where a woman falls for her abuser. But he needs to have actually done something to earn it. This feels surface and shallow. Why would she go searching him out after all that. She should have taken 200 years to forgive him or else he should have sacrificed his life to turn back time... This is... Boring and completely unbelievable.