I can't really add anything to what has been said already, but I would urge you to stop cheating. Take some time, think about how you want to live your life. If necessary, make a clean cut and re-invent yourself, but you shouldn't exploit your partners trust in you.
I agree with the posters above me. This has nothing to do with a poly relationship, this is simply abuse. Unfortunately this guy is probably a sociopath and wherever he goes there's chaos and destruction. I had my fair share of this kind of people in my life. There are so many red lines (that...
I'm not a big fan of dating websites. Too many frauds, too many people (men) who are desperate to get laid. What's even worse is dating websites creating fake (female) profiles to get more clients.