midfieldace.......At 55 you still got some good years ahead of you. Luckily your children are all grown up. They might better understand now than if they were younger.
You say that there has been no intimacy for a long time but that YOU fell out of love with her many years ago. Do you think she doesn't feel that ? What can you expect ? Also if you were the one to always instigate intimacy, even from the beginning of the marriage, that should have been a hint of how she felt about intimacy and things to come.
She surprised you by seemingly mentioning divorcing, off the cuff several times after an argument or disagreement. And yes , if you live in the U.S. she does have the upper hand in a divorce court. Depending on many different factors of course.
But your vow to stay the course because of YOUR parents divorcing usually doesn't carry water. They can feel the tension and may feel different than what you may think.
Lastly you say your ready to move on. It seems like both of you would agree to a divorce, being honest and open about it.
As far as hurting her feelings, I wouldn't worry so much about that because that sentiment may not be reciprocated.
Best to you , ( and start looking for a good lawyer ).