Yael,
I have felt so many of your feelings. The thing I have to remind myself of, though, is that the wishful thinking I have about wanting someone to share building the picket fence with is just that--wishful thinking.
If he had been there, he wouldn't have been interested in building it with me. He would have thought it terribly corny and silly and a waste of time. He would have demeaned me for it.
Either way, if he were still in my life or not, I would have had to build it alone.
I'm a few years older than you and have been my own husband and wife a few years longer. I wish I could tell you it gets easier. That has not been my experience. For some of us, especially those that grew up without a healthy role model of coupledom, you have to give up a lot of yourself to make being a couple work.
It may be that being alone as much as I have was the only way I knew to preserve myself. Or it may be that I'm just unlucky. Or that, as a good friend once said, my "picker" is broken. Whatever it is, I don't think this life is the one where I fall magically in love at 70 and have a few good years with my soulmate. Maybe... I don't rule it out.
Sharon