I've been married a long time and am now in a situation where most of the time, I feel the relationship works well. However, I too have recently had counselling for some OCD thoughts and it has been recommended that my husband and I might benefit from relationship counselling.
I asked him, and he agreed (after I had explained about the fact that some of his actions, even though they occur now quite infrequently, were triggering my OCD).
It crossed my mind, at the time of asking, what I would do if he refused. I'm not sure of the answer, but I think, given I have identified that the dynamic of our relationship is affecting my mental health, that I might have had to consider leaving the relationship if he didn't agree. I didn't spell that out to him, but it was in my head and it gave me the strength to tell him just how important it was to me that he was willing to engage with the process.
It strikes me that perhaps you need to consider leaving if he is unwilling to engage in the process of trying to mend your relationship, which is clearly dysfunctional. It's impossible to guage, from what you have said, whether more fault lies with one or other of you. And to an extent, it probably doesn't matter.
He says he doesn't want to leave. But if he wants the relationship to work, I think he needs to engage in whatever activity is required to make that happen.
I find it very frustrating when people admit there is something wrong, but refuse to put any work into changing it.