You didn't fuck up when you were with him because you didn't dare do anything that would incur his wrath but, even though you had become his puppet and did everything he wanted, he would still find fault and reason to be angry with you.
You've effectively been in prison for, what, 15/16 years?. The majority of that time was spent in lockdown and what amounted, effectively, to solitary confinement in that you were only allowed to speak to those who were on his'approved list'.
During this time you became institutionalised; told when to go to bed, when to wake up, your endless days and nights of incarceraton planned for you and inscribed on tablets of stone by your jailer - he who had to be obeyed at all times.
It's not surprising that you're struggling with life on the 'outside' but, as time goes by, you will become accustomed to the sweet taste of freedom; to being able to do things your way and to being able to operate an open door policy for your friends and for those of your dc.
Reach out to the friends you have and make new ones. Join your local Gingerbread group www.gingerbread.org.uk and get together with other single parents.
Look at further education opportunities in your area and take advantage of all the help you can get from SS to further your ambitions.
The harm he has done you will take time to heal but you can and you will 'get over him' and I promise you that, if you stick with it and resolve to do your utmost to give your dc the life they deserve, there will come a time when you'll shudder at the very thought of him.
There are a lot of good people living close to you - get out there, start socialising with them and hopefully, one day in the not too distant future, you'll find a good man who'll make you realise how very badly you were treated by a sick, twisted, pervert, and how very wrong it was that you and your dc were subjected to such tyranny.
Please note that I'm not urging you to rush into another relationship but I am advising you to have the fun and enjoyment that comes from mixing with kind and considerate people that you missed out on while you were in his control.
Every time you look in a mirror, look yourself in the eye and affirm 'I am a strong and confident woman' and 'I am all things to myself'. Say the words out loud and repeat each affirmation 6 times.
You've broken his hold on you; stand firm and make sure it stays broken, honey. I say again - you can and you will do this, and you'll do it because the alternative doesn't bear thinking about.