Yep, he was just a plain old liar and cheater using the idea of poly as a cover for having no ethical integrity. People who are good at lying can be very charismatic and often don't seem to know when or how to stop.
I'm sorry you fell prey to someone like that, and I'm glad for you that you're moving on. That is in no way what poly is actually about.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.