I'd like to welcome you here, my heart goes out to you when I read how hard a life you have had, getting the most horrible of situations, abuse as a child, lack of support from an alcoholic mother at the time, rape, and a highly abusive first husband. Then supporting a second, followed by the death of your boy. To cap it off physical problems and hospitalization.
I'm not sure from your post if the last man, the mostly good one, stayed around.
OK, it is small wonder you have gotten worse and all your symptoms ramped up to a peak.
I can only give you a few words about my own story, which has a mostly happy ending. Yes you are in a bind BUT the real you is still inside, and as you proved before, you are capable of very great improvement, plus there are medical professionals who "get it" and genuinely help.
Lastly there are good loving steadfast partners.
MY PTSD, depression and anxiety did not come from the same sources a yours, but the symptoms sound much the same, plus, like you I lost someone closest to my heart.
I guess I was luckier and after being suicidal for some time told my partner, and then had a series of medical professionals until I got a psychiatrist who understood, and when he moved I got another.
Being overwhelmed by past events, sleeplessness and nightmares, thinking that is too heavily influenced by the past are all still there, but their force has been much muted, I avoid obvious triggers and live a pretty good life. When my first partner died I married again -to a widow, and was blessed with another strong understanding partner. I rely upon here for perspective, she relies on me for other things.
So no I honestly don't think you have to accept the real you is locked away forever, masked by the injuries life has given you. In time, with support you can heal. That does not mean the grief over your son will leave, he will always be part of your life, but in time only part, like my first wife.
You have love inside you -for your kids -you do not tread them badly as you were treated badly yourself, you rose above that. You avoided the drink, you expect marriage to be good, you have the fortitude to take what life had handed you and simply need to believe there is hope, which I'm trying to give you.
Although we are not identical I understand a lot of what you feel, you are welcome to talk here anytime.