Is this a control issue? It sounds like you want to control how your husband deals with his depression, so you had a big fight. By leaving the bed, he makes a statement that he will deal with his depression as he sees fit. Now he's ready to move past that, but you want to control if he leaves the bed or not again. How can he promise he won't want to leave the bed again? Maybe you guys will have another blow up over his efforts to deal with his mental health and he will again feel unable to share the bed. I personally would never want to force a person to sleep in my bed. If he needs space and needs to sleep elsewhere, is it really helpful that he sleep in the bed and be miserable and feel controlled? His response to you that sleeping in separate beds helped him to cope sounds like an honest one.

I think also you are sending your H confusing messages. On the one hand, he tries to resume sleeping in the same bed, and you tell him he is not welcome. And then later, you tell him he cannot leave your bed! It would be confusing and stressful going to bed every night--who's going to be lying next to him, the wife who doesn't want him there or the wife who won't permit him to leave?

It sounds to me like the bed issue is a symptom of a rocky time in your marriage, not the cause. I agree with 50guy, get some counseling quick to try to work this out. The longer this battle goes on and the "chasm builds between you", the harder it becomes to get back to harmony. Hurry!