I like keeping all my history in one place, so there is a postscript to my tale.
After J sent me the email telling me that our relationship was over, I was puzzled, since the last time I had talked to him, the day before, we were flirting a little and talking about going hot-tubbing together. So I wrote to him and asked what had gone amiss. I expected that C had just put her foot down once and for all about me. By the time I got a reply from J, I didn't have the heart to read it, I just forwarded it to my husband and asked him to tell me the gist of it. He said that J. said that he had decided to end our relationship because I had written to him, the day before, that his wife was still angry and resentful and that made me sad. Since she'd been shouting at me in the middle of a restaurant on and off for three hours straight not three days prior, I thought my observation was pretty much spot on, but J. took what I said as unfair criticism of her. At that point, I decided it was time to step away from the crazy and I did not reply to J at all. I did not block him from contacting me though. He tried to get in touch with me via IM less than a week later. I was too upset to talk to him, so my husband interceded and told him I just wasn't ready to be in touch with him yet.
While I already knew I did not want J as any kind of platonic friend or IM buddy, I figured that eventually he and I would settle down to be civil and polite in public places, if nothing else.
My husband was not satisfied with what he knew about what had happened. It didn't add up for him, that J. had discussed getting together with me and then dumped me barely 12 hours later. C was still writing to my husband, mostly hostile emails trying to get him to concede that everything that had happened was 100 percent my fault and she had no responsibility for anything that had happened. For some reason, even though she was a condescending bitch to him in her emails, and even though he'd caught her in a pretty outrageous lie, she still seemed to want him to have a good opinion of her. I urged him to block C if she was upsetting him, but he wanted some answers, so he asked her a few questions. She told that J had been writing a breakup email to me WHILE he was making plans to go hot-tubbing with me, that he had no intention of following through on those plans, and she made it sound like they were actually LAUGHING at me while he and I were IMing. Also, that he took my interest in hot-tubbing with him as soliciting sex from him, even though I had explicitly said that sexual activity was not permitted at the venue and one could actually be banned from the place for violating that rule. I was nowhere near ready to be intimate with him, and I thought I made that clear to him, but he preferred to think otherwise (his ego was way bigger than another part of him, apparently), and led his wife to believe that too.
My husband could not believe that J had really toyed with me like that, so he wrote to him and asked if it was true. He said that J. didn't deny any of it.
At that point, I blocked J from being able to contact me online in any way, shape, or form,and even blocked his phone number. C was already blocked. My husband hasn't blocked them yet, but I think he's pretty close to that point, since C. is still sending him poison pen emails, two months later, squawking that he has no right to blame her for what happened. Some people just can't let go, I guess.
I don't quite understand how I fell in love with someone so vile. I feel like an idiot. But it's made it easy to get over him. I don't miss him or any aspect of our relationship now. I'm just glad it's over. I am hoping that my husband and I don't trip over them in this very small poly world of ours, but if we do, we will just ignore them both.