man, it sounds like you're really getting shafted here. 5 years of keeping someone financially when she has repeatedly taken advantage and told you hands-off sounds like a prison sentence.
What do you get out of this? Your needs are the most important thing for you to evaluate as you make this decision. What you have described is not poly- just sounds like you're being scammed.
I suggest you erase her manipulative ideas from your mind and think about what you would like to see happen in your own life. If you don't think she will love you and help you get there, then you are holding yourself back from the opportunity for happiness outside this confusing relationship.
I have been guilty of cheating and lying myself- so I'm not on my high horse about that- but if there is no desire to make amends, work through it, and find happiness together- connection, deepening of love, true concern for one another's well being and growth- than it's just time to move on, and believe that if you do the right thing for yourself, others will do right by you.
"Rocks will open and make a way for the lover."
~Hazrat Inayat Khan
I love Catfish and Charlie.