But he has these spells where he sounds like he just about can't stand me. He pretty much lets me know, from time to time, that he wishes I would just shut the eff up. Sometimes it seems like he finds it annoying to listen to me when he's watching TV, which is whenever he's awake. He needs help for every single thing, as I've explained in threads before. He can't get on and off the toilet without help. I've been telling him he better stop snapping at me, or I'm going to leave. Yesterday morning was like the final straw.
Sometimes, I see no way to untangle myself from his problems. Maybe I'll wind up worse depressed, walking away from him. It will be just one more thing I fail at. That leads me to awful thinking.

Rose76-
It all sounds so heartbreaking. You need to put yourself first somehow. My spouse sometimes gets impatient with me about some things so I understand how that feels. It can get quite toxic--you need long breaks from this.
I had surgery on a finger Tuesday (I am typing w one hand). They gave me 20 hydrocodone/acetaminophen which I took ever 3 hours for one and a half days. All I could do was lay around. I was making even worse decisions than usual. I could feel it pushing me down into depression. I am telling you this to say in order to improve your life, you may need to stop the vicodin. You say it helps you sleep--but vicodin induced sleep is not quality sleep. Perhaps, in addition to a stimulant (I take 150 mg bupropion a day)--he could give you something to help you sleep. Being more active will help too! I know it is not easy because your burden is so heavy. I think you need to run away for a while!
He tells me not to hang around, if I don't feel like staying. He says that I can leave and he'll be just fine without me. Maybe kis kids and the authorities will just leave him on his own to rot here. In this senior apartment complex where he lives, they find people dead in their apartments on a regular basis. No one seems to think that's any big deal. They'll offer him "Meals on Wheels," and tell him he can stay here with just the attendants coming around. He'll wind up covered with feces. Sorry for that graphic, but that's the reality. So, even if I leave, I'll have that worry on my head.
I think you should just inform his kids, him and everyone who cares for him that you are in crisis and have to leave for at least a few days! Hugs! Don't give up! Keep posting!