It may not be someting that you are or were doing. In fact although we all contribute to our marriages in many ways, nothing is usually just the fault of one person.
You mentioned that he was depressed while owning his own business. Now he is happy with his job. That is a step in the right direction. But it may also be a sort of awakening of someting in him. He thought the depression was all about the job and maybe now he is realizing it wasn't just that. It may not be any one specific thing causing those feelings but in looking for a reason for it he may now be focusing on his home life. I don't want to say he is still depressed but in my experience with depressed people (and I've had a lot of it), it sounds like that may be a part of it. Just something to think about.
Still reread the book. It will give you a good idea how to start to get yourself on a better plane than you are right now and even though you don't want to lose your M, all you can do is take care of yourself and see what sort of impact it may have. Is he willing to go to counseling?
Where does he want to emigrate to and why?
If you focus on the past, you ruin the future. You can only live for today.
