Hi Trish
I know you'll be feeling really torn about this.
The way I see it - the best place for you is where you are - and the best Trish you can be for your family is gonna come out of what you're doing there now.
Its putting the oxygen mask on you first so you can be together later.
Leaving there, going back to the same old situation, however noble the intent - forget about our opinions, can you honestly say to yourself it's gonna be any different?
The fact is Trish - you have a pretty large extended family. You're doing what you need to do right now...if your grams needs help it's time for someone else to step up to the plate.
Failing that, are there any community services available? I know I get help cleaning and stuff for a nominal fee. There must be options like that around?
You have an enormous heart Trish - but think this through carefully - this isn't about being selfish, it's about becoming who you need to be
big hugs
D