Sure, it probably would have resulted in an affair but maybe it didn't and I'm just worried if I go to this stalker status and get caught then I've lost all her trust as well and at that point, I would agree, whats the point of being married if you have to go to that level?
You just do not get it. Sex or no sex with the OM, the other man (OM) has a relationship with your wife that is inappropriate just by virtue of the secret communications. Sex or no sex with the OM, getting drunk at bars and coming home at 3am is not acceptable behavior in a marraige. Sex or no sex with the OM, your wife is spending too much time with a toxic friend that is getting a divorce and is using your wife as her wing-man as she hunts for men. Sex or no sex with the OM, you wife told you that she sees you as more of a friend or buddy rather than as her husband, this is cheaters code for I love you but an not in love with you. Your marraige is in big trouble already, so you need to stop letting your fear of taking the wrong action stop you from taking any real action, because doing nothing will eventually mean the end of your marraige anyway.
In marriage proving that your spouse has not had sex with some else is not a prerequisite, for you demanding that she start acting like a married woman. Demand the following:
1) Full no contact (NC) with the OM.
2) To verify this NC, she must give you full transparency with phones, computers, text messages, etc. Tell her that you will give her the same full transparency because, except when going to the bathroom, married people do not have a right to privacy from each other.
3) No more acting like a single person and going to bars etc without you.
4) Since the toxic friend that is getting a divorce was party to her relationship with the OM, and is using her as a wing-man as she hunts for men, she must end her relationship with this toxic friend now.
As it is heading now, your marraige is probably over. Taking action now is your best chance at saving it. It may already be too late, in which case you will finally know and can move on.