A) Please tell me you have seen an attorney already? If not, see one ASAP. I wouldn't just trust his claims that he hasn't done anything funny with the money - trust but VERIFY. Ask him for copies of all the account statements if you don't have them.
B) Why separation and not divorce? It's different in different jurisdictions, but in my state, getting a legal separation was going to be just as much work as a divorce, and would have to all be repeated (at extra cost) once a divorce was decided on.
If I were you, I would see an attorney ASAP and figure out what is the best course of action FOR YOU. Don't worry about him - any extra money you can get from him is money you can protect from OW for him, if he ever comes to his senses.
Also, separate the emotional from the business here. Being "nice" to him in the negotiations will NOT increase the possibility of him coming home. Be civil but work to make sure you get what you deserve. Don't let yourself me short-changed just because you don't want to make waves.
