Saying one is poly does not prevent one from being an asshole. I wish it did! There are honorable poly folks out there. This guy isn't one of them. People lie, shade the truth, leave out critical details. And sometimes people use poly as an excuse for bad behavior. You have a much better handle on what poly really is than he does. It's still lying and unacceptable. You sound like you realize you need to dump him and move on. That is exactly what you should do. Chalk it up to a lesson learned.