Final weeks with Mom; so lost, mad, confused, lonely. Please help me hold on...

My Mom is in her final weeks with Stage IV breast cancer-- she is 72, I am 44. I lost my Dad to prostate cancer in 2003-- he was 63, I was 31. To say I HATE cancer is about the understatement of the century. But here we are-- my Mom is probably 88 lbs; is on hospice (despite this being a bit of a battle with her); has swollen legs & feet that weep & a distended stomach (due to liver failure); is bald yet you can see several small brain tumors on her head; sleeps about 20 hours/day (although she has trouble getting comfortable since she's so thin & her bones jut out so much) & is oftentimes depressed or tired, at times angry, frustrated, etc. When I'm at her 3400 sf+ house I'm given a huge list of chores to do (wash dishes, make meals, go get groceries, vacuum floors, clean hardwood floors, make bed(s), strip bed(s), water plants/trees, dust, do laundry, feed dog/exercise dog) & of the rare times she's awake & coherent our talks are short & always sad/tearful. I live 1.5 hours away & between myself & my brother (who lives 20 minutes away) & her sister, who just flew out from Hawaii last week, we're caring for her at home (with her sister doing the bulk of the care now since she's living there). I'm at Mom's house 2-4 days/week & call daily if not several times a day when I'm not there (she rarely answers or returns my - or anyone's - calls). I work full-time, have a 7 year-old son & husband & am finding it near impossible to juggle her/her needs & the necessity of being away from my family to care for her with some slice of my old/normal life. Our fridge is near empty, house is a pig-sty, laundry piles up, bills are barely getting paid on time & I'm doing a 1/2-**** job at work, despite loving what I do. I fight each day to maintain control & not get undeservedly upset with my child or lash out at my husband but, there is a part of me, admittedly, that's 'mad at the world'. 

I feel guilty always, every day-- like I'm never doing enough for my Mom or wondering if I'm "supposed" to quit my job & move in with her & dedicate all my time to care-taking her, rather than still continuing to work, be with my family, see friends now & again, etc. Truth is, I don't want to be there 24/7; it's exhausting & intense & sad & she's down & gets angry if we tweak a pillow or mattress the wrong way & cause her discomfort... I'm sure I'm a horrendous person for admitting all this. Funny thing is, all her close friends are retired with little to do & when I approached them about perhaps chipping in 1 day/week of care they all said no-- but these same people will judge me & my brother & our presence (or their perceived lack of) at her home. 

I don't know what to do. I don't know what I'm 'supposed' to do. I don't know if I'm making mistakes & they'll be ones I'll regret or if I'm being smart & exercising some ounce of self-preservation by allowing some time away to run my regular life. It's worth noting that I offered -- many, MANY times for my Mom to move into the guest bedroom at my home so I could, indeed, take care of her 24/7 & still do what I need to do, but she refused. It's also worth noting that her health is so bad I think she should be in a hospital with proper beds, toilets, medical professionals but she's chosen to be at home - has no "long term health insurance"/never made or discussed her desired long term plan - so this has fallen at mine & my brother's feet. 

I want to breathe & feel more in control of this difficult period in my life. I want to stop talking with every person about her cancer, the latest changes & updates on her health-- & I want to know how others navigated all this... I'm so lost, so lonely & consumed with guilt.  Any stories, advice, suggestions deeply appreciated.