Good morning Quadro, I think your comparisons and jealousy (?, not the right word but don't know how else to say it) of your ex stem from the fact that your dreams were shattered when things didn't work out for you. You are grieving for what could have been when you see him pick his life up just like that while you are "sat at home drowning in washing and parental responsibilities he is shirking his and galavanting around". I can totally understand this.
However, and forgive me if I'm harsh, I think your view is very skewed. This man has hurt you in numerous ways, chances are he'll do it again. After all, you are away from him now. Chances are it's her that will get battered.
So he has found someone else. That happens, good things happen to bad people, you cannot control this and herein lies the actual problem: you still look at what your ex is doing. He should be non-existant to you!
You need to find a way to focus on your own life. Living well is the best revenge. Ignore him as much as you can, don't compare yourself to him or the new GF. Don't stoop low to their threats or whatever they do, keep a dignified silence. Go out with your friends, re-assess your life: are there things you wanted to do but got side-tracked by your marriage? Would you like to learn a new skill, find a new hobby? When thoughts of your ex come in and you see red, think about it for 5 minutes, allow yourself to picture why he is an undeserving tosser and unhappy POS and move the thoughts aside. They are not healthy and once you learn to focus on new things they'll come less and less often.
He's controlled you in the past. Do not let him influence your future! Good luck!