Just wanted to welcome you to our forum.
You make some interesting points, and it is often felt (by poly folks) that polyamory is, first and foremost, an emotional thing (while not ruling out the sexual). I'm personally of the mindset that there's something of a slider between "how monogamous" or "how polyamorous" different people are by nature. I'd almost say you seem like a "very poly person" who's been with some "very mono people," but actually it sounds like your monogamous partners were just plain possessive and insecure.
If two people happen to be monogamous and enjoy relating to each other emotionally to the exclusion of others, that's (theoretically) okay as long as both people feel that way. But when one of the two people longs for outside (such as deep/platonic) type friendships, it seems like the other person should be willing to compromise a little and allow for those friendships. There are ways to be wholesomely monogamous, but monogamy isn't for everyone. The problem is that standard social beliefs are that monogamy is for everyone.
I can agree that polyamory seems to be a perfect fit for you. I guess we can call it emotional polyamory when it doesn't result in a sexual relationship, but the point is, you needed the freedom to just let the various relationships in your life be what they are.
Anywayz ... glad you could join us, hope you will feel at home.
Love means never having to say, "Put down that meat cleaver!"