I think like you mentioned there are a lot of contributing factors to why this is going on but understand the frustration as well. I'd recommend, limiting his area and re-potty training him as if he was never trained before. so going out every couple of hours, as soon as he wakes up before bed, etc. Puppy pads may be a good idea as well to save your floors. With all the change that he has experienced lately it might just be a timing game, retraining, and mitigation until he understand, feels more comfortable and feels better. I hope this helps!