Well I’ll be honest with you and say “Neither did I!” All my learning about rabbits came AFTER I got my 1st rabbit. Lol
It sounds as if you’ve got a double whammy of causes for his loss of habits. The move, coinciding with a neuter. Some rabbits will actually get worse just after neuter but this does settle down. Given it’s only been a 1.5 weeks, I’d say hang in there and allow some more time.
I first thought about making his space smaller to retrain him (he runs free), but he gets SO STRESSED when I put him up!! I bought a baby gate and he can scale that in 5 seconds!! So I got a second baby gate and put it above the first one. I put him in a spare bathroom. He refuses to eat and just lays around looking so sad!!
Sorry to say it, but it is probably best he is restricted. This is what you would do for a pre-neuter bun that has lost habits, or one in a new territory that has lost habits. He may still mark with poop when exploring new areas once allowed but this should resolve by itself. If it’s full on peeing and pooping, go back to square one. Smaller area.
I know you may feel bad about doing it but it should only be temporary. I think it helps to think that a lot of new space might be overwhelming to a rabbit. That they feel they have to mark this big new territory against potential intruders. So restricting the space may actually help with their sense of security. Does that make you feel less guilty?
Is his habitat in a living area where you spend a lot of time? If you can be in the same space, giving attention, giving occasional head pets and treats as you go by, he may settle about being confined.