I'm sorry to hear you're in this tricky situation. It sounds like you've moved on from that relationship and you have the full support of your current husband, which is fantastic, but now you are unsure about how to maintain this old friendship.
I understand your ex boyfriend is quite alone in his mental health issues, and you still care about him and want him to get through it. This puts a lot of pressure on you as, possibly, one of the few people who is actually supporting him. Can I suggest you have a quick look at this page I've linked below, if you haven't already? It is really important to make sure you are mentally well because it is nearly impossible to support someone in a helpful and healthy way, if you're also not coping. Unfortunately, the stress of supporting others can really creep up on us.
I think the direct answer of whether your support is overall helpful or not, is going to depend on a lot of factors so it is quite difficult to know what to do. It may not be healthy for him to be overly reliant on you, and he needs to have a wider network of support people. But at times, people who are really struggling will need to lean more heavily on certain trusted individuals like yourself, so that is to be expected as well. I think my advice here would be to see what his doctors are suggesting, and if that aligns with your goals as well, to encourage him to work through that professional advice.
What are your thoughts? It sounds like you've given this a bit of thought recently.