A long one, abuse aftermath

I wanted a bit of genuine feedback, no nasty or hurtful comments please. God knows I have bashed myself about what I am wanting to vent for nearly 20 years.
I have left a relationship of eighteen years, this was two years ago. In the time since, I have met and are soon to be giving birth to my first child with an indescribably supportive, phenomenal man, who fulfils my every emotional need, builds me up and supports and protects me. I have moved an hour and a half away from my children in order to do this, they are not ready to make the move yet, in spite of my desperate hope that they will soon.
I met the father of my first three children eighteen years ago. The abuse began pretty quickly after, running the gamut of every kind of abuse there is. Physical, verbal, emotional, sexual, financial. My family and friends could not fathom why I was putting up with this, trying to help me leave, trying to reason with me, but the very immature, naïve young girl I was believed I was head over heels and I could fix him. My son, now nearly eighteen, came along when I was almost eighteen myself. I left his dad for the first time in 2004, after realising the verbal abuse was beginning to reach towards our son, three at the time. I came back soon after.
Deep, long lasting crippling depression ensued, me not being able to deal with the way life was panning out, in a constant state of walking on egg shells and extreme anxiety, keenly studying my husbands body language, verbal cues, and desperately trying to do anything to fix it when I could hear the warning signs. Resigning myself to the fact that sex was a daily chore to be endured, never entertaining the possibility of denying or airing my own wishes as on the rare occasion I tried, that results in wall punching, knicker ripping, denigrating words spoken. To this day I cannot, absolutely can’t deal with confrontation, that familiar eggshells feeling making me want to be sick.
Things getting to the point where I had my own very strong mental voice, emphatically agreeing with what my partner was saying, that I was a useless fat whale, terrible in bed, ugly, having no function in the world. Nobody loved me and if I died everyone would be better off. Having concrete plans all worked out with myself before my second and third child were born, to drown myself in the bathtub after taking a heap of pills while my firstborn was at school, having someone pick him up, and my family raising him. That voice is still there sometimes, but I was already working hard to squash her before I finally left him, so she’s fairly quiet most of the time.
After my third child was born, I had a mental breakdown. Unable to cope with anything but simple daily tasks, my partners mother took my second soon daily so I could cope. They formed a bond, what turned out to be an odd, incredibly close symbiotic type relationship. I bitterly wish daily that I had been strong enough not to need her. I was strong enough by the time my son turned three but by then it was too late. He was sleeping over many days a week, my older son confiding in me that she used to bribe the younger son, saying “You don’t want to go home to mum, if you do I am going to throw out all your toys and I will find another little boy to love”. (she had a whole shopful of toys she brought just for him, my older son and my daughter always forgotten).
To this day my son lives with her. I do not get informed about doctors visits, school absences, the recent autism diagnosis that was always fought form the start, her too ignorant to realise a proper diagnosis would only ever help the child, that it is not a stigma like long ago in her day. They sleep in the same room on bunk beds, her partner relegated to the couch. He only recently, at my insistent behest, started washing his own hair, dressing himself, and taking care of his own needs. There is no impediment in that aspect, he is highly functioning and a smart little cookie. The vitriol my son spits at me when I pick him up for fortnightly visits is all her, brainwashing.
I was held down as much by her mind games as I was totally destroyed by her son. She always telling mt things like I was never meant to be a mother, and that we owed her for her help. If I had killed them both, and spent a decade in jail I would be in the same spot I am now. She legitimately helped at the start, but crying carrying on, and making life hard while I still needed her when the kids were little, in order to go out and make a living, I was torn and had no idea what to do.
My kids are told all kinds of lies about me, how I cheated on their dad multiple times, he tried to kill himself because of me, dad never hit mum but mum made all kinds of trouble for dad with the police. My son flat out believes it, my daughter questions therefore she asks mum. I have endured, survived so much from this pair but they continue to put the screws to me in whatever way they can. It infuriates us, we have started court proceedings, soon to initiate mediation, but have been forewarned that this will take years and years. How can I cope with all of this? Knowing that my kids are in such an unhealthy environment? Being fed lies? Having the whole nasty saga played out within their earshot, hearing things like “Oh isn’t it nice when she can pick and choose when she wants to be a mother?”, “These kids wouldn’t know anything or be anywhere if it wasn’t for me”. My kids even tell me things such as her brother, a convicted paedophile, currently incarcerated, didn’t do it the girl lied. There is a well known history of paedophilia in the family.
She plays it out to our small town as if she’s the grandma rescuer, raising my kids while I ran away. Telling schools and medical professionals the same thing. Having this persona of loving, happy grandma, professional angel, who gets along with everyone and is really no harm. Even my family believe to some degree. Even fake nice to me when it suits, her belief that she can keep me lulled into a false sense of security. The nice granny persona is rapidly falling off as I take more action, she knows the jig is up.
Am I selfish for moving away, to find happiness with a man, the absolute love of my life, who has brought life back to my existence? Who has brought back my self- worth, my looking forward to things, to making me enjoy every part of life and feel so massively loved? Should I have kept on where I was when I met him, (he can’t move to where I lived, job shortage is phenomenal, he did try trust me), working three jobs and not seeing my kids but when that harpy dictated I could??
I love my kids, but nobody in my life understood what it was like, having escaped brutal abuse but living in an empty shell it left, waiting and holding out until the kids grew up, my fervent belief that that was all I was still alive for, my kids, and the pain it would cause for them if I died.
I read this, as an escapee, and I cry, I am so close to the perfect life now but I feel the gaping wound of not having my kids with me.