I will only say this. No matter whether you move home or not, if you rock his boat on something else and he doesn't like it, he will threaten D again. I would call his bluff and if he files for D, let him. Mlcers like to make threats about divorce because it's the only way that they can get the spouse to back off. You do realize that there is no guarantee even if you remain in the apartment that he won't file?
No one should have to leave their home unless they are being abused or someone is threatening to kill you in your home. If he's that unhappy, then he should be the one to leave, not your or your son. Right now, he can tell others that you left because you weren't happy and not the other way around. Right now, if he were to file, he could say that you abandoned the home and marriage. We know that's not what happened, but they do love to twist words so that others believe that we are the reason for things happening the way they do.
When you move home, look to his as a roommate, no expectations. Continue to live your life as if he's a renter, nothing more. The more you try to tell him what to do, the more he's going to do things, just like a two year old who tries his mother's patience. Again, it can be done, but you have to be determined to live your life and keep your focus on you and your child. As for him, well, he'll be sleeping on the couch on the guest bedroom and I don't see him going anywhere because his mission is to stay in the home and block you from coming home.
You and only you can determine if you want to reclaim your home. I wouldn't let anyone tell you what to do, especially that husband of yours. I would take some time and think about it because you and your son really do deserve to be sleeping in your own home, in your own bedrooms and w/your pets. But, that's my two cents.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.