A, Your three reasons for why some of they do not request a divoce quickly are good ones. However, I also think that if you leave them alone, as you have, they do not feel like they need to lash out and end the marriage quickly. The more you push, the more they will shove back. You've left your h alone and he's felt threatened in the sense of needing to keep you away from him. You've allowed him the time and space he required to work on himself, or should I say "grow up".
Many do not reach out until much later...why? Depression and withdrawal, i.e., they go hand in hand. I wouldn't be too concerned if you didn't hear from him for long period of time. I didn't hear from mine for over 2 1/2 years. Then, because of the circumstances, he begged me to be friends w/him. We touch base periodically now, but the conversations are usually about family and when he inquires about me, I tell him I'm fine and do not share anything of my life w/him. He knows he royally screwed up, but unless he's willing to do the work, he'll never see the light of reality again.
They all have the same script and use it almost word for word. Actions are a bit different, but the script is always present.
A, I think you doing very well. Age has no bearing on being single, i.e., 60 is young in today's world. When you least expect it, life will offer up some adventures and surprises for you.
