Well I have to say I impressed by your thinking. You are approaching this in a healthy way. Even though the start of your introduction to poly was one based on betrayals.
A lot of us have that person or situation which looks like crap on paper, but was our into to poly. Mine was falling in love with a FWB my wife and I were sleeping with (we had been open for years). This failed miserably and in fact caused me massive amounts of pain, and personal growth.
Without that kick in the teeth I would never have met my ex-gf. Who has been one of the most loving supportive and influential people in my life. I owe her a lot, including my life. Poly allowed me room to have this person in my life.
Welcome and continue reading. There are lots of resources, all with slightly different takes and explanations on what poly is. There is a whole range of what it can be... so remain open and enjoy the journey.
And of course keep us updated.