OP, your situation sounds horrendous and I have much sympathy for you. I was, and still am in a number of ways, in your situation.
I was on anti depressants, my ex is a controlling, abusive prick, my teen has been acting up in many, many ways. i work full time and carry the can for everything. I'm exhausted.
BUT, I'm 2 years down the line. here's what I did.
I stayed on the anti depressants, until very recently.
I took all the help I could get from friends and social services. I cast off feelings of shame about it, and talked openly about everything that was going on. I needed help. The teen and I are in family therapy with CAMHS and it has helped me enormously.
I listened to all advice about coping strategies and being kind to myself. Some worked for me, some weren't suitable in my circumstances.
I'm now with a lovely man who is calm and patient and his approach is infectious, he calms me down by example and listens when I'm ranting.
So, my advice would be to do what you have to do to get through this phase. You're clearly self aware enough to know your approach is wrong, and you behaved badly in the incident you described. But try to forgive yourself, work out how you'll handle things differently next time and move on. I don't think i could have mustered a patient response when confronted with what you had to deal with this morning. Lean on friends, seek professional help, particularly if the kids are acting up, they'll need the help too. Actively seek out calming friends and activities.
You are not your ex, you're under an enormous amount of pressure and this situation will pass.