Just one more to the “you and the kids have to leave” chorus. Leaving the children in that environment just sounds entirely unconscionable.
Don’t you DARE leave those kids!
You may be 100% sure she’d never harm the kids, but you also tell us she’s crazy. She may very well be just crazy enough to hurt them - you don’t know. Don’t put yourself in a position to find out, either.
Take the kids, leave and move in with your family. Your kids are gonna be royally fucked up if you stay in this environment - if you get out now, they may have a shot at ending up normal.
Get out. Now. You know what you need to do, you’re just “stuck.” Get unstuck.
You need to talk to someone who isn’t on the internet. Just because she won’t go to see a counselor (as you have apparently tried) doesn’t mean you can’t talk to a professional alone.
My 2 cents worth:
Call a domestic abuse hotline.
Call social services and/or similar for your area.
Call the police when she is abusive. At the very least they will document the event.
Call any other government service in the phone book that looks like it might be helpful.
Call a counselor you like and go, alone if necessary.
If my father up and left me with my clinically insane mother, I would never, ever forgive him. You think your kids don’t realize her problems, but I assure you they do.
Take your kids. You’re their father and it’s your job to protect them with every last ounce you’ve got in you.
Talking with the law clinic at work is a good first step. It doesn’t sound like you are living in a crisis right now, so you have time to arrange an orderly disengagement from this relationship - disengage yourself from the lease, make arrangements for you and your kids to live somewhere else, arrange for a way to make money and have childcare, start the proceedings for a divorce, all those things. No, you can’t just disappear - you could if you didn’t have kids, but you do. They don’t get left behind with a mentally unstable mother.
If the children have been witnessing the meltdowns and verbal and emotional abuse of the OP, they have already been hurt/damaged/harmed. They are, however, young enough that recovery doesn’t seem insurmountable. While you’re contacting abuse rescues, lawyers, shelters, and your family, don’t forget a little counseling for the kids.
Wow! Thanks for all the replies, everybody. I agree that it would be unconscionable to leave the burritos with their mother. I won’t leave til I can take them with me. I had a lapse of character to even consider it, but the moment of blind desperation has passed.
As to their current mental state, my wife almost never does anything in front of them, except use a shitty tone with me. She behaves fairly well as long as I maintain the fiction. I dont ever talk about anything remotely threatening while the kids are present. They never knew I was leaving. Twice I called from work, while they were at school and once I picked them up from school after telling my wife that I wanted a divorce. When I picked them up, I told them we were going on an adventure and they had the time of their lives at a hotel with me until I fucked up and revealed where we were.
I looked up some domestic abuse info and learned something that had never occurred to me. It is considered abuse to manipulate someone with threats of suicide. Who knew? She hasn’t attacked me in months, because for the most part, I just walk on egg shells and lie and work my ass off to keep her functional. Work was insanely busy today, thats why I didn’t post til now, but tomorrow I’ll make time to call domestic violence helplines and see what my options are.
Also, I do see a therapist, and my son spends time with a counselor at school a few times a week due to his autism. He is highly functional, well behaved, and smart as a whip, but as long as we can get the service for him, we intend to get it.My daughter is very expressive and she comes and tells me when she is upset about things. So as unlikely as it might seem to any of you not currently living in my fucked up house, I have shielded them as best I can and will continue to do so.
I’m committed to escaping as soon as is humanly possible and I’ll do it with the burritos firmly in tow.Thanks again for being with me while I figure out how to make it happen.
Bolding above mine - yes that is abusive and manipulative! Domestic abuse goes beyond hitting, a lot of it is rooted in control of the partner, one way or another.
Glad you’re going to keep the burritos 
in mind through all of this.
It sounds like you’re making good plans, El Burro. You probably know this, but it doesn’t hurt to hear it again - you are not responsible for your wife’s mental health, and you can’t help someone who won’t help themselves. Sometimes, people we love can be like a drowning person - you’ve done all you can to save them, and if you stay with them, you just get pulled down yourself. It’s not a bad thing to save yourself and your kids.