OP, I hear you. It is easier sometimes to talk to anonymous strangers then it is to talk to people in real life. Although, you are going to get a lot more rudeness through anonymous strangers and I'm sorry about that.
I'm sure that you've taken the time to read through all the post although, this discussion has really gone long and there's a lot of post to read through. But even if you only read through your own, you have to see a pattern here.
You say that he's controlling, that he's irrational, that he's judging, that he calls you mean names like Scag and slut and irrational and stupid,
That he's been doing this for at least 6 months,
That you're happier when he's not around, that you don't live together,
That you think you have low self-esteem and you think that you'd rather be with someone who is constantly hounding you, constantly judging you, constantly mad at you about something that they have no business to be mad at you about, as opposed to the idea of "being alone"
Being on your own is not the same as being alone and it's not the same as being lonely. Yeah I know that there are times when you feel grateful to have someone else that you can talk to or that you can spend time with, but when you talk to this person and every conversation is loaded, and when you spend time with them and at the end, you feel trapped and you can't wait to be away from them... You see where I'm going with us?
You're a little bit younger than 50, you're not exactly put out to pasture.
And even if you were 93, who cares? You sound like an intelligent and introspective and interesting person. You may feel that you don't have a lot to offer a potential partner (and apologies for circling back to your original question but I hope that STIs are not something that you could be offering a potential partner, any chance that's possibly what this guy is on about? Have you guys been tested for any infections? That would be my primary concern with a new partner, not how many people they slept with, but making sure that it's safe for me to sleep with them...)
Seriously. You sound like you're too good for this guy. You really are.
You don't deserve to be hounded and berated and belittled and judged and shamed by him based on how many partners you've known intimately over your years of being a sexual adult. Infections aside, it's none of his business, it has nothing to do with keeping secrets or being dishonest, it's about him controlling you and judging you and prying and snooping and even if you gave him 100% honest answers with photographic backup, and a written testimonial from each partner that you had, that wouldn't be enough for him. Hed continue to harass you and then he would just pick something else to make you feel bad about.
Screw him, but not literally.
Don't screw him, get rid of him.