I too am a victim of domestic abuse and it stepped up massively when I decided to leave. But there are some things you really need to do to ensure your safety and the safety of your children. Everything and I mean everything needs to be logged with the police. Every time he harasses you (3 unwanted texts in 6 month period is harassment) every time he hits you, hurts you, threatens you, wrecks your things all need reporting and most importantly followed through. Don't drop any charges. You need a paper trail. Every time he hurts you take photos of the damage, go to hospital if needed and get it reported.
You need this evidence. You need it so when you apply for a child protective order (so children remain with you as main residence until they are 18) and any child arrangements order made for the children after the court has a full recorded history. Otherwise it's he said she said. And believe me I feel that he is going to be hell in court.
Also when I reported my abuse I was allocated an IDVA who was amazing she told me what I needed to do practically in terms of court orders, living arrangements, she put me in touch with a solicitor, and also some incredible counselling.
You are going through hell, it's not going to end for a while- but believe me it does eventually end and you will be happy again and you will have a good life again.
Accept all the help you can from pil. They seem like wonderful people.
Also I would reconsider giving Deenas husband evidence. He needs like you to be able to move on. You didn't destroy their marriage she and you husband did. But he to is a victim and he needs to be able to move on and have the freedom to be happy again. The evidence doesn't have to be everything you have on them, but just enough to help him. She seems to have a history of cheating on him- she's managed to win him over and get him to father a child that isn't his. So this time he probably needs the strength from proof.
Fir me it went on for two years- but after reporting and reporting I finally got away, I'm now happily married and have a wonderful life. This is not the end of your life but the beginning of a whole new chapter which starts off really rubbish but it will have a happy ending x thinking of you x