I would suggest a copper iud as a mostly foolproof non hormonal contraceptive. It shouldn't affect libido, and fertility returns to normal immediately after removal.
It's my experience that you can't force the feeling of commitment or wanting kids. With my ex, I was always unsure, didn't really see that future, even though we had been together a while and lived together. With my current partner, I know that's what I want, we have talked about it, and it feels right to be making these plans with someone who is totally on board with our shared goals. Anything less than that degree of commitment and uncertainty is unfair for both of you. As you said, she's approaching the age where she needs to find a life partner to have kids. If you force this, you probably will never find out what it is to build a mutually satisfying partnership with someone who is compatible in all the ways that matter.
From the inside, you probably can't see it, but to everyone reading what you write and the subtext, it looks like she is jerking you around to get her way. She has her goals (ring, marriage, kids) and she sees you as a provider and sperm donor. Are you going to settle for a relationship where the only sex you ever get is out of duty or to make kids? Are you going to settle for a woman who won't try to meet you halfway on your desires unless you pay her off with a ring?
Its harsh to put it that way, I know. But your responses are somewhat dodging the real questions you face, and circling back to what she wants every time. Put yourself first, because you can't make someone else happy by sacrificing yourself.