Hi Beety, thanks for the update.
Obviously it's hard to have a feel for what point your husband is at, or rather where the 'line' is for when an intervention should be beyond his permission. For thinking about this we should consider a few things:
If your husband is getting worse, is it in a new way, in a way that hasn't been experienced before? If what is happening is completely new to him, and yourself, intervention may be necessary.
It may be worth asking him: at what point do you think you require treatment/intervention? This might prompt to to reevaluate the state they are in. You can help them understand this state. For example, if he is behaving or feeling a way that's new, and more extreme/worse than before, then asking them where the line is might help them realise this. If an answer isn't provided; as in they don't know, or don't care, then it's simply another sign that involuntary intervention is necessary.
It was good that you checked regarding self-harm. Often instances of self-harm occur in harsh episodes of grief, shame, and a highly-elevated emotional state, where rationality is out the window. If you feel your husband is getting close to this stage with his behaviour, I would advise contacting our BeyondBlue emergency services. Or alternatively, contact a hospital's psychology department, and inquire about arranging a home-visit from a doctor/GP (who is familiar with mental disorders, obviously). This brings the intervention to him, and may remove the hurdle of going out to deal with their issues.
To recap, we have a few things to consider: taking note of new experiences that are alarming; asking what they think their limit is, and use this as an indicator of how they are (if the response isn't convincing, then move forward with the following consideration); contacting emergency services if the behaviour of your husband is endangering himself. This can be physical harm, or it could be an extreme remission into clinical depression, which often requires immediate hospitalisation.
It's hard when we (possibly) come to this stage, but what I've mentioned above would be the last considerations before action is necessary.
Once more, get in touch with BeyondBlue emergency services (chat online, or call 1300 22 4636) to confirm what I've said.
Also, I could be wrong in my interpretation. The state he's in may not be as extreme as I perceive. Still, I hope what I've said makes sense, and that you'll respond in the loving way you have thus far.