Most Helpful Guy
First remember this... he did not abandon only you... he walked away from his children. His actions towards you are a reflection of his inner feelings of himself in a way. He is a very unhappy person and he is taking his anger out on you... which is no excuse to treat any human being like that. If we, as a nation, treated the terrorists in prison the way that he is treating you, we would be deemed to be torturing them. Change your cell phone number so he can't text you any longer and if possible, move out of the area before he takes it to the next level and you and/or your children suffer a terrible fate. You can also file charges of intimidation against him with the police. Get over him... there are too many guys out there that would love to be with a woman that is wholly dedicated to them... and they will treat you like a Queen.
Most Helpful Girl
The thing is that we can't control our feelings. Of course, it would be better for you to be able to forget about him and not be hurt by what he's done and how things have turned out with him. I think it's easy for us to say that you shouldn't feel bad and be glad that you got rid of him, but the truth is that you have two (soon three) kids with this guy and you were with him since high school. So obviously he is a big part of your life and naturally it makes you sad, even if he is objectively an asshole. Even if deep down inside you know you're better off without him. I think what you need is time and you will see that it will hurt a little less as time goes on.
One more word about the pictures of cows he sends to you: have you told the police about that? If not, you definitely should since he still harasses you despite the fact he was arrested and charged. You should document everything he sends to you end give it to the police.