OK, Waiting, I'll try and answer the questions in your OP.
I do know it's not normal in a way but do people put up with it because it's 'their' normal and that's just how my life is?
Yes, you're right, it does become your 'normal'. That's why we call it "normalising abuse", this process of making excuses and blaming yourself and thinking if you just did this or that, maybe it wouldn't be so bad. It actually does become your normal. When I was 17, my school friends told me their dads didn't thump them. It was a massive shock - to me, it was normal to get thumped. I assumed all men abused their wives and children.
Some people wil have non of this going on for them so to them it's a big NO that's wrong, others maybe it happens , there told he's going to kill them?
Yes. Again, my dad told my mother he would kill her one day. She knew he meant it. Once, my brother and I pulled him off as he was strangling her. He told me he'd kill me, too. As I went to sleep at nights, I used to think up ways of defending myself against the various attacks I thought he'd try.
My first husband stopped hitting me after I left him briefly, moving on to emotional abuse which I didn't recognise for what it was. He still had a violent temper, though, and would say he'd kill me. I didn't believe him. Many years later he came into the room where I was sleeping and strangled me.
So what I'm saying is: I know what you mean about it becoming 'your normal'. But the fact you've got used to it means nothing, really, the threats are still meaningful. When they say it, they will do it.
I have no idea if I'm making any sense?
It's like this, I think ... The part of you that knows this isn't all right, and you have the right to live safely and calmly with your children, fights against the other part of you that has normalised the violence. It gets all twisted up in your head, along with the blame and the excuses, so you almost feel as if you're living in a dream sometimes and nothing makes sense.
You can get so used to it that you really can't imagine life any other way. After Dad died, Mum dated some men who were nicer than him. I had to coach her through accepting that decent men do nice things for you without demanding some humiliation in return, and that you don't have to tiptoe round decent men's moods. She had completely lost her view of what really is normal!
My father was a sadist along with his other lousy qualities. I picked up on this in later years, and Mum has now confirmed it. From what Izzy said about your previous threads, I'm guessing your ex is one as well. For these people, it's not like a BDSM game; they genuinely find it arousing and amusing to cause pain and fear.
Just because they like treating other people like cats treat mice, it doesn't mean you've got to be their mouse! The mouse suffers injuries, intense pain and fear, then dies. The cat walks off and forgets about it, it's not grateful to the mouse or has any feelings towards it at all.
The world's full of decent people who don't hurt others for fun. Live in this world.