OP, I don't want to write your username, because you seem anything but worthless. You have been a wonderful mother, a devoted wife, run a home (I presume as you have a traditional set-up then he has done very little around the home over the years) and have nothing to be guilty about or feel worthless for. If my DP treated me only half as horribly as your DH does you, I couldn't bear to sit on the same sofa as him, never mind just 'give myself up to him'. The way he speaks to you and treats you is emotional and verbal abuse - and who on earth could willingly give themselves to an abuser? You are a normal, mentally healthy woman who quite naturally and rightly recoils at the thought of having to do something so intimate and loving and giving to someone who is treating you like shit. You are in the right here.
What you say about writing letters struck a chord with me, because I've recently read a thread where one poster, trying to help the OP said that she'd regularly sent her abusive DP letters trying to explain things and her counsellor had told her that if you're at the stage of having to send letters, then things are in massive trouble.
I do think your husband is emotionally abusing you. I have been in an EA relationship and everything you say about his behaviour and your reactions ring true (mine never wanted sex as a way of making me feel repulsive and as though no man could ever desire me). They destroy your confidence, you doubt yourself all the time and you start to truly believe everything is all your fault, even though you can simultaneously see that he's in the wrong. I was with my wanker Ex for 7 years and found it v hard to break away, even though the love had long died, so I totally understand how hard making big changes must seem after 30 years. Your whole identity as an adult so far is being this man's partner. But concentrate on this: your identity SO FAR. You are still a young woman, and clearly one of intelligence and insight, with a big heart. You deserve so much better than this and your children will be being damaged by seeing their father treat their mother so coldly, nastily and cruelly, with so much disdain and blame. And before you beat yourself up about that, that's his fault, not yours.
When men act the way he does, many counsellors don't like to see couples together, as emotionally abusive men refuse to accept their right and will try to manipulate the situation. Your DH has already come out with nonsense about the last one being a 'lesbian feminist', which reveals that he is going to find bullshit excuses to not listen to anyone trying to work with you both and also reveals some nasty and very old-fashioned ideas about women. I think you definitely need counselling for yourself, because, in your heart of hearts, you know this is over. His fault, not yours.