cebeast, patience sounds like the best path for now. It's like my friend and her boyfriend - they are taking it slowly, one day at a time, even though their relationship has been happening for a few years now. The relationship is a balm to both of them, even if they haven't taken any steps to sharing a home or getting married. And sometimes that's as far as it can go. If you have the 'whatever-it-takes' to stay around, you could be a wonderful grounding support for her. It is very easy to lose perspective when all your attention is focussed on your kids, especially the problem ones. You can lose yourself, find yourself submerging your own identity and putting too much of yourself into your child. Not good for the child, not good for the parent.
If you commit to the point of "can't back out now" there can be a sense of resentment - either in you, for feeling that you shouldn't have taken that final step; in the partner, for worrying that you will feel resentful and resenting you for feeling resentful, even if you're not (if you follow); and in the child(ren), for daring to trespass on territory where they don't feel you belong. And they will throw it up at you to win points in an argument.
But if you're on the scene and simply waiting, and if you and your girlfriend are OK with this, that can work too.
Ant'sMom was right - this truly is a matter of taking things one day at a time.
And what are your alternatives? If you wait, and if your relationship can stand the tests ahead, you will still have a wonderful deep relationship even if by then you're mid-fifties. If you say sayonara and move on, how long will you be alone? Will you find someone as good? Better?
John Lennon said it well in "Beautiful Boy" - "Life is what happens when you're busy making other plans."
Throw your plans out the window and just live.
And good luck, whatever you decide. You are you, this situation is unique to you and girlfriend. Others have similar experiences with a wide range of differing outcomes.
Marg