I can relate

I think time will tell - if you can take some space from the guy, you might see & feel things differently. But I think it takes a couple months at least to get over someone. I was hypo all summer. Broke up with bf, had to sell my business, went a little crazy. Totally fell for this younger guy way too fast. Really got mixed up between sex & love. It lasted a couple months, but he rejected me. I was just a bootie call. I stopped responding to his late night texts & it was really hard, it really hurt my heart. I got back with the long term bf. Seemed to be best for my youngest son, going back to school & bf is a good steady influence on him. I'm a mom, my life isn't about me right now, it's about my kids. I feel saner now, somewhere between depressed & stabilizing.
I feel guilty a bit for hurting the bf. But to be honest, the hurt & confusion I have now are more like, What was I thinking?? What all just happened, how'd I let myself fall for a guy like that so fast, how'd I let myself get hurt? 2 months no contact with him. I saw him at a bar a few weeks ago, he dismissed his other ladies like he always did and made himself available for me (cuz you know what a good time we bp'ers are!), but I stayed sober and drove my gf home, said Bye. So now, some space, I'm almost over it. I will always have to live with the memories & close to the best sex I've ever had. Started to feel hypo recently, and he crossed my mind, but i'm not going there, I can't let myself fall like that again. I don't even miss him now.
Anyway - I think time will tell if there's a potential future and relationship for you with this guy & it's time to leave husband. Or, was it the hypo/mania... It takes time to reflect on all the things that just happened. I don't think trying to be friends is a great idea, I think you'd be prolonging the hurt of saying goodbye, hanging on to the possibility that it would turn into something more.
Hang in there. Hopefully the feelings might fade and you fall back in love with your husband (if that's what you want). I know how hard this must be but consider going "no contact" with the lover for at least a couple months to clear your head, and figure out what you really want.