Sheenie,
So sorry you're in this position. It's very like one I went through years ago. When my mom became ill with cancer she mellowed somewhat, but my Dad became more hostile than ever. He expected me to fill all the needs (this from a man who'd had almost nothing to do with me most of my life) and never was appreciative of anything I did do. Thank God I had an aunt who lived close by who helped out tremendously or I don't know how I would have survived, physically or emotionally. Mom was sick with cancer for two years and went through multiple treatments, it was pretty awful. But at the time I hated my parents so much I didn't care what they were going through and the things I did do for them I did totally because "it was the right thing to do". I had a facade that I developed as a child that I used when with my parents, it was the dutiful, respectful, child facade, but there wasn't any love in it---there was lots of rage and hatred that came out as a coldness but the real rage never came out, it wouldn't have been acceptable. I just played the part, begrudgingly, until they died. It was hard, it was horrible and all the years of putting up with their abuse and stuffing my emotions nearly destroyed me. I admire you that you've been able to separate yourself from your mom to some degree and have found some measure of self-worth and independence.
I can't tell you what to do in regards to caring for her. Your plan of going for a short amount of time sounds good. Yes, your brother will blame you for not helping out more but then would you ever really be able to do enough to satisfy your mom or your brother?? Only you know the answer to that. At what point does your own emotional survival come into play?
One thing to think about, is your own guilt that you will experience after your mom is gone. Because that guilt will come, or at least it did for me. I certainly wasn't expecting it, but it came and then I was glad for the things I did do, even though I did them for the wrong reasons. Of course you've already nursed your mom through one episode and it sounds like you did quite a lot for her. And if you're on the east coast and she's in Texas, then I'm not sure how you could really be there that much anyway. You have a lot to think about, but it sounds like you have a good perspective on it all.
I'm glad you've come here, to this forum. I hope that you'll find some comfort and guildance here.
Adrift, with land in sight