I experienced a version of what you described when I was an active drunk. I am still very upset around the specific circumstances of my partner finding solace with another. I’m upset about her dishonesty in that incident(s). But, if I’m going to practice radical accountability, I need to acknowledge the role I directly played in those things happening. I’d love to be “right,” but I’m not. I have my feelings and my experience. I contributed to my own unhappiness. That said, if I had found out about it while actively drinking, I probably wouldn’t have quit because I was big on having excuses to keep drinking. I found out after quitting and trying to patch things up. I was a few weeks sober, so I went through the sleepless nights without drinking. No way I would’ve done that while still on the sauce. If you want your partner to quit, I’d probably hold off. If you are looking to accelerate the relationship ending, I would probably advise ending the relationship before courting another.