Hi, SH. I just read through your story and can identify in so many ways. We too had a great marriage for the most part. I never doubted his love for me and he was so good at taking care of me and then the MLC . . .ick. The thing that really resonated about your thread with me, too, is that even when things were peachy my H did share a lot about old wounds from childhood and admit I probably kind of brushed them aside. I did listen and validate, but I guess I just didn't realize the depth of the damage at that point.
My MLC H lives at home (though "separately") still. If your H does decide to move home again, my advice is to give him as much space as possible. Stay out of his way. Let him fend for himself (as Snodderly pointed out). Be kind but detach! If he is in MLC he will most likely act differently and do things you have never seen before (like you said with the detailing of the car, etc.). Just do your best to focus on you and not him. It is a tough road and it is a long one.
The advice you will receive here really is invaluable - there are so many wise posters in so many different stages of the journey.