the same thing is kind of happening to me as well lol. I would say try to plan chores and where everything will be going ahead of time in order to feel more organized and get a better idea of what’s going where. the small things are definitely important (like silverware, who’s doing groceries, budgeting, etc.)

helping him keep a sense of familiarity by you being around and filling your new space with familiar personal items. what’s helped me feel really at home after moving to collage was having my dorm filled with my stuffed animals, books, art, and posters from home because i’m also really sensitive to change as well but it feels much better to have made the space like my room.

It honestly sounds like you’re already doing everything right! Change is inevitable but having set plans and routines will help a ton!

I think an idea that can help is hanging out overnight with the two of you guys multiple times leading up to it, so he can get used to it little by little, I think that can really help him. For example maybe you guys can plan a trip or just stay at a hotel for a couple nights to simulate living together.