Drained...I understand why you are feeling this limbo of not knowing for sure which way you should go. I've been there because when I divorced my husband I did it with love in my heart still beating strong for him....still does. He said a lot of things to me that made me feel guilty....made me feel unsure of my decisions....but it all affected me because I allowed it to. Because I made room for him to manipulate my emotions. It is tough to metaphorically fight through the garbage...the quacking and the manipulation. But it is possible. Find the time to have some quiet contemplation where you are listening to your own mind and heart. Figure out what is best for you.
As far as the ultimatums...I've given them...it is a kind of control and there is just no way no matter how much you try...to control the actions of another human being. I ultimatumed my husband into rehab twice...meetings...outpatient. They never had any lasting effect because the stints weren't meaningful to him. I too, at the time, thought he would "get it" just by being there.
The simplest way I could put it is...every lesson you learned as a teenager and as an adult, think to yourself, was it learned from the advice of others or learned from your own actions and consequences? Did you defy the advice from your parents only to learn later that they were right because you again took action against their advice and suffered a consequence? Same with addicts. They need to make the decision on their own and even when it is made on their own recovery is tough on them. I never whole heartedly did something from the advice of my parents because it wasn't what I wanted to do. Eventually I ended up doing what I wanted to do and ended up paying for it one way or another.
This is why....
Release yourself from his addiction. Allow yourself to do what is best for you and live life and at the same time let him live his and figure out his own path.