Girl, figure out a way to either 1. block him from access here (sign out and change your password/username) or 2. get past whatever you think will happen if he reads the TRUTH about himself, and take care of you.
That's what you can do for your little ones. I learned that the hard way. Sacrificing myself so much that i'm not well, is NOT good for my kid. Take care of you! Since this is a 'have to' situation, try not to think about it as 'leaving'. You're not. You're going out to get a massage, or a mani/pedi, or have a girls night with a friend. Things that all Mama's single or married or partnered, take time to do. Try to see it as not a big deal, and just one of those things that Mama's do to keep their sanity. (in fact, this WILL help you keep your sanity. i'm not lying!)
It's tough. i KNOW it's tough. But you can do this. For yourself, and your little ones. Take a deep breath, figure out a way to have the support system you need (which includes MDC!) and just know that you can do this.
Your best bet with DS is just to acknowledge how he's feeling. "Yes i know you miss Daddy. You will see Daddy when he comes to visit tomorrow night." etc. It kills me when my DS cries for Daddy, whom he doesn't even know (and it's usually when DS is upset with me that he's crying), but i hug him, tell him it's ok to miss Daddy, and that he'll be able to talk to him on the phone later that night. I know it doesn't sound like much, but it's simple, and the best thing you can do for your children is just to BE there for them.
Hugs to you Mama!