I would wait a few weeks and then follow the suggestions in the Bonding section in the green banner above under INfo and begin a very gradual new bonding attempt in a neutral place, like a bathroom or hallway. Humping is OK as long as it’s not on either one’s face. It is their way of trying to establish who is dominant, but be prepared to not let it go on long – water bottle to spray, and a net strainer if you have to break them up (gloves too.) I agree that the hormones may have been active still, but it’s been a couple of months now.
This may sound odd, but did you own them and have them altered yourself, or did you acquire him as an already neutered bunny? If you didn’t take him, it’s possible that he wasn’t done properly, or the previous owner misinformed you. (People have been known to do that to unload an animal, I’m sorry to say.) It would make more sense if he turned out not to be neutered properly. Just a thought.