Did you try a couple of years ago before you had your second child or just after?

It sounds like you have a relationship of sorts - not what you used to be or want necessarily but you have chosen to remain living together and act as a family. You haven't told anyone IRL.

You still have him in your signature on BB which seems at odds to being completed separated, but living under the same roof.

Is he is your boarder? Maybe you need to go through the process physically and mentally of making this more official?