Hi Shelly77 and welcome to Beyondblue.
You have a lot of emotions going on there about various people in your life. From what l gather, your husband is causing you the most angst which in turn affects the relationship you have with your step son. Obviously, your husband has a parental responsibility to address his son's issues, and he is hand balling this to you. You have been and still are generous and giving of your time, so both his ex and your husband are accepting that you can carry the load. I feel it's time to get all parties on the same page and communicate the issues and your concerns for you are not the only adult responsible. By accepting the role, you have set a precedent and being taken advantage of. Of course, l need to hear both sides to under the full story, so my commentary is solely on what you have provided.
In relation to your step son, due to his age and circumstances, children only act out when they are hurt or have not been guided by parents on the right and wrongs of life. I am not insinuating that you are to blame here, but if your husband nor is ex-wife are addressing behavioural issues, etc as they are the biological parents, the child will have little chance to develop good behaviour.
So for your mental health and that of the child, all adults need to talk this one out. Like l said it is not your sole responsibility.
Concerning your marriage, have you asked him to go to counselling together? Relationships Australia offer some great options to get things out in the open and deal with the issues that you have around intimacy and connection. Google them for details.
I do hope l have been of some help Shelly. Please write back and let me know how things are going. We want to hear from you.
Carmela