But it doesn't go down with all of us that we're just going along with something to please our partners or doing something despite our partners' reservations.
@NeonKaos, I completely agree.
DH, I have always felt multiple in my love and desires. Society forces us to choose monogamy or pressures us to not enter into committed relationships if we refuse. Heteropatriarchal supremacy rules, still. Personally, I've rejected marriage despite making commitments because I didn't want that extra layer of expectations on me. I've never been in a mono/poly relationship as you describe, although there were periods where it may have looked or felt like "mono," but that was out of desire for it, not compulsion.
I'm new here, don't know all the backstories and such, but here are some thoughts.
Relationships are work, they're joy, pain, security and risk. I've lived and worked through the full spectrum of amazingly wonderful to incredibly hurtful over the years.
From what you've said, it sounds like it's just not healthy for you to be in your relationship any longer. I'm struggling with that question myself, but not from a place of lashing out. What can get you to that place of peace with yourself to really think about what your needs are? Of evaluating whether what you have is really right for you? It sounds like you're afraid -- of losing her, perhaps of not finding another, I don't know.
Honestly, I think you're wrong to blame poly or non-monogamous relationships. And, "restless heart syndrome" -- the name implies that it's an illness. Multiple desires is not an illness. People grow and change. The issue is about you and your wife and what you have together. I would guess many of those issues would be there whether you were poly or mono. I agree some of the lines she gave you sounds like BS. I've never liked that kind of talk ("you can't meet all my needs" etc.), it doesn't seem honest. I'd rather hear, "I like this person and I still love you." From your side of it, she doesn't sound like she's taking you into consideration. That's not cool. Bottom line though is you need to do things for yourself and I don't mean that in a being selfish way, but in a what is important to your happiness way.