I don't think she is faking the letter.
Cassandra, don't give up on yourself, yet. Just because you are 43 and feel you have a "trashed body" doesn't mean that you are unloveable and unwanted by anybody. You feel that way-- but you are most likely wrong -- your feelings may not reflect the facts at all.
I'm sorry your husband is as dense as a "brick" -- meaning that he is just behaving as a stone wall and refusing to accept your communication of your feelings and needs. This can be the most lonely feeling in the world -- that the person you most need to understand you is refusing or unable to do so. That really hurts, doesn't it -- and tends to make one feel angry.
My only advice is this: your husband is not to blame for everything that has happened to you or gone wrong in your life -- and if you need his understanding and support, you will not get it if you attack him and try to make him feel bad or guilty. To protect himself, he will be a "brick." (people resist feeling awful about themselves -- especially if they are men, I think). I wonder if you are confusing your feelings about your abusers in early life with your feelings about your husband?
Is there any way to communicate with him in a non-accusing way?
Good luck -- but whatever you decide, please know that middle aged women are not ugly, not un-sexy, and have plenty of life still left in them!