@howcanhedothis18 my heart goes out to you 
You sound so much like me. When I look at how I let people treat me I go between feeling ashamed (when I should not) and being upset someone who was supposed to love me, was supposed to be my 'other half' could use my lak of confidence and self esteem.
You've had really good advice on here re. the legalities and PLEASE believe me when I say this will all be worth it.
If your poor Granny (bastard him doing that her!) had already noticed you were, for want of a better phrase, a 'people pleaser' (this was always me...now only to a tiny extent) then being with someone like him has dragged your self esteem down to the ground.
HE has been complicit in your lack of confidence. He is acting erratic, you will get through this and get what you deserve in the settlement and have a lovely life with your children.
He knows he doesn't have control this time, that's why he is doing this and undermining you. He can't control you divorcing him so is trying in other ways.
You will get through this my lovely and be sooo much better for it, you just can;t see it yet.