Hugs to you. I feel a certain amount of anxiety on reading your posts.
The description you give of R pushing to get you to agree to start swinging reminds me of the old Kantian thing about how to treat others. Kant said that people should aim to "act so as to treat people always as ends in themselves, never as mere means."
By that he means that everybody is intrinsically valuable and so we should avoid treating them as tools through which we can satisfy our own goals.
It reads to me as if R is using you as a means to his end of engaging in swinging. (apologies if I have misread you).
In general, I would feel very uneasy about anybody who would try to push me into doing something new that I had expressed anxiety about. I would find it hard to consider a person who would do that as trustworthy - I don't know that I could trust that person to be considerate of me once we were engaged in the new thing.
Are you finding it possible to connect with people near where you live who are not involved in your relationship? I feel like you might need a bit of a support network.