First, welcome. Sorry you find yourself here. A couple of quick things:
1. Have you read Divorce Busting or Divorce remedy?
2. You are correct to stand your ground on staying, but let him have his space. Continue to NOT start relationship discussions.
3. This is going to be a process that will NOT be fixed quickly. If you are looking for a line or a magic bullet, there is none. A rule of thumb is for every year you have been together, there will be a month of repair. So buckle your seatbelt, this will be a ride.
4. Do not bring up your theory is is suffering from depression or that this could be a MLC.
5. Cristy is correct, a DB coach could help with guiding you through this. And if not A DB Coach, at the very least get yourself into some Counseling (marriage or individual).
Me: 43 M: 10y S:15 ILYBINILWY 2/18/13 W moved out 2/18/13 Filed for D: 2/17/13 Got DB: 2/20/13 Got DR: 2/23/13 180 & LRT Began: 2/25/13 D Final Dec '13