I am willing to be some kind of mother for him, but it can't be a full-time job
Looking at what I wrote then it seems I already understood the emerging dysfunctional dynamic (and there were many already!) in our relationship and that it was unhealthy for both of us. More importantly, I realize that
I was not acting like an equal partner in the relationship either. Though it felt good (at first) to think I was offering the love, counsel and wisdom of a supportive partner, I realized it was as much about my attempts
to control her behavior which did not feel good then, or now, to admit.
I was absolutely devoted to the distorted idea that by 'helping her grow and mature' that we could have an incredible, supporting, trusting and understanding relationship with an unbreakable bond that was forged through:
Solving problems (i.e. me solving problems for her and not allowing her to learn to problem solve for herself)
Building trust (i.e. teaching her what trust was in effect removing her from the adult responsibility to determine this for herself)
Helping her to become a better parent (i.e. removing the responsibility for her to learn what this is for herself)
Helping her to manage her emotions (i.e. controlling her)
In short I was not helping her, or myself, but doing the exact opposite. I was hurting us both. It's been very humbling and uncomfortable for me to admit that in thinking I could support her this way that I myself was not acting like a healthy, functional adult who wanted to be in a relationship with an equal. It's okay though because it's allowed me to reassess and relearn some important concepts going forward about what type of r/s I would like to live in and what type of person I need to be in order to do it. Life is a process, yes?

So in your case, Triss, when you say "I am willing to be some kind of mother to him", have you thought what this means to you?
Yes, I agree a 100% that you can't have an equal, adult r/s this way, which is one of the reasons why I quit... .
but I do think it's not bad to try to support him as a friend, and hopefully our friendship can evolve to a certain level that grows above me being a "mother" and him denying all responsibility... .
at this moment he really got major problems (as in: no job, no home, no official adress, no money, very troubled relationships with his family, huge addiction problems)
since he lost his house in that fire 4 years ago he became some kind of an outlaw and it's clear that he really is not able to get out of it by himself, this situation is so complex that it's way beyond his capacity to handle it on his own
I have been trying to get him into health care and after 6 months now we finally came to the point that he has been talking to a social assistent from a psychiatric unit, so there is a chance he will get appropriate help at last... . still, the final word has to be his and I know he has a huge fear to get institutionalised and an even bigger fear for being sober... .
so in answer to your question: I see my "mother" role as
1. providing him some attention and motivation to go on with this
2. reminding him of his appointments and I try to keep the contact with his stepmom and this social assistent so he would have a small network of people he can trust
3. and I admit I do some very "motherly" things like doing his laundry and cleaning after him, and preparing some food when he comes along, but it's not my intention to keep on doing these things for the longest time, and in return he helps me with small jobs in my house so that's fine for now.
one step at a time, but I do not doubt it a second that he will be gone the moment he finds a replacement