He's cake eating. He has both of you wrapped around his finger. Nice gig for him. Don't be an option. That's too disrespectful to you. You don't deserve that. You're being strong, which is good, and you said you won't be a plan B, which is also good, but then you allow him to have his cake and eat it too AND keep kissing, hugging, and telling a man you love him THAT IS ACTIVELY CHEATING ON YOU WITH ANOTHER WOMAN.
If you want to save your marriage, you have to stop doing that right now. Read about the 180 and employ it. I can tell you have the strength. Some of it may seem counter intuitive but it works. It's not guaranteed but it does work better than anything else you'll try. Trust me, I know.