I have no experience of divorce but didn't want to read and run.
You have been through a lot emotionally. You have been worn down over time. It could be that you're still grieving. Yes, a relationship breakdown is like a form of grief. You had dc with this man, you married him. To you, you took your vows and commitments seriously and it is a huge shame when it doesn't work out even with all the best intent in the world.
The counselling as you say has opened up some past wounds about your childhood and life. No doubt this will play on your mind from time to time. Does your new partner offer you emotional support? Or have you a trusted friend or confidante?
You have been through a lot, 18 months isn't really that long. I read somewhere that when a relationship dies it takes half as long as you were in the relationship to actually get over it. But in truth some people never get over it.
I hope you find closure op, you also need to be kind to yourself, you have gone through so much. Just remember that the man you married turned out to be emotionally abusive and is the reason why things couldn't work out.
Give yourself time to feel what you are feeling. When it hits you, allow yourself to wallow in it for a while. But don't stay there, find something fun and positive to do afterwards. Remember you have the rest if YOUR life to look forward to. Fill it with the things you love.
Hope you are ok, I wish you the best 