Problem with boyfriend’s past behavior

I’ve finally started dating someone a little more seriously after two years of being single following my divorce in 2018. Everything was going well, and he had told me in the beginning of our time getting to know each other that his longest relationship after his first college girlfriend was an affair with a married woman who he still keeps in touch with a few times per year. This affair ended more than ten years ago. When he told me initially, I felt a major sinking sensation in my stomach followed by a tightening in my chest. In general, my body closed off to him. I did some models on it and told myself that there were offsetting qualities to this undeniable red flag and that I’d continue to date him to see if this relationship with his ‘ex’ was going to be a problem. We have continued dating. While I like him, this affair he participated in makes me disqualify him as a marriage partner. I don’t think I want to get remarried anyway. People in my age range have too much baggage (including me) and I don’t see any financial benefit to the piece of paper or protection since I don’t have any kids. I’ve been married and lived the Disney princess fantasy, and I’m over it because I don’t think people nowadays are fully committed to the institution. I put my all into my marriage and got burned because my ex husband was never fully committed, so now I just don’t think anyone is worth that kind of commitment and time. Plus, I don’t think most people have the relationship resume to pull off marriage, so I’m fine with casual or serious dating without any goal of marriage. I have explained this to him. He has never been married and I think he wants to be while I’m firmly against on account of the prior affair. I realize it’s in the past, but that behavior is not in alignment with my ideals or interests. I don’t think he would really understand commitment or the sacrifice it takes because I think fucking around would always be an option for him. My ex husband also participated in an affair prior to our marriage, and it affected his commitment mindset. I don’t want to go through that again with someone else, and especially not in a marriage. Although I am dating and having sex with him exclusively, once he told me about his prior affair, I did not delete my dating apps and feel no guilt for wanting to keep an eye on who else could be out there for fun and diversion. I haven’t told him this, but I think that his prior behavior would probably make him sympathetic to my point of view. Truthfully, I could never fully trust someone who hasn’t respected the boundaries of marriage by participating in an affair. I enjoy dating him with no end goal, but I feel that he wants more and there will never be a point where I will relent to marrying him. I am struggling with whether to leave the relationship altogether so he can be open to finding someone else who can be less judgmental and more accepting of his past moral failures than I know I will ever be. I am really struggling with whether I can change my thoughts to accept his past affair partner/current friend into my life. I don’t really want to. The only thing I want to feel in this scenario is some clarity around the situation. I know it’s a manual issue to tell him that I want him to stop his friendship with this former affair partner, but I’ve been spending a lot of energy buttoning my lip to avoid telling him to do that. The only path forward to marriage for me is if he gets rid of her altogether. I know this is sounding more and more like an ultimatum, but I don’t see another happy path where the three of us are sophisticated and laughing over expensive wine about how complex relationships can be and isn’t it great that you guys had an affair? I don’t see that happening. I’m not that evolved and I’m okay with that. I feel like all the guys in my age range have some fatal flaw and I don’t think there’s much hope of finding anyone better than him. I do like many aspects of him. He’s caring and sweet and a gentleman. I’m having trouble committing to him after learning this and I’m spinning in confusion. I’d like to keep looking for someone else whose ideas and past behavior surrounding commitment are more in alignment with mine. I don’t want to give up my ideals, but I know that changing the circumstance isn’t the answer. I don’t know if I should stick it out with J and do the thought work required to get okay around the prior affair partner/current friend and feel like I’m compromising my values or move on because I know it’s not going to end in marriage unless he kicks that woman to the curb and never looks back.