Support/advice needed- my father's battle with pleural mesothelioma

I'm on the brink of mental collapse. I don't know how/if this will help but even temporarily, I just want to offload in the form of written word vomit..

The backstory:

My dad was diagnosed with advanced malignant pleural mesothelioma in July 2016, despite having never worked in construction or served in the military. He is an enthusiastic DIY-er so suspicions are that in doing home repairs on our old house he may have had minimal asbestos exposure. He exhibited telltale signs before diagnosis; shortness of breath, pleural effusion, etc.--in short, the thoracic surgeon went in to remove a "4mm abnormality", and instead found widespread tumors along the lung, lung lining, and diaphragm. It has been a little over 6 months, and after 30 sessions of radiotherapy and 2 cycles of chemo (carboplatin/alimta/avastin, which was deemed ineffective) it has since spread through the diaphragm to the liver and up the chest wall. He also had(?) a rapid emergence of a second cancer, dedifferentiated liposarcoma in a football-sized tumor on the back of his right leg. That was diagnosed and surgically removed in October, so we have been focusing on the meso as it has more potential to be fatal. 

I am 27 and the middle child of three daughters. My older sister (29) has had a tumultuous relationship with my parents, so although she is sad and affected it's in a distant way. My younger sister (19) is still very much a kid, and seems not to have full comprehension of the situation.

My mom is distraught. I expected this, but not to the point where she would be unable to function. The night my dad was discharged from his first surgery, he experienced some complications, seizure-like tremors, chills, etc. My little sister was home and called 911 as my mom's only reaction was to hug my dad and repeat "don't die, don't die" in Mandarin. I realized that to a degree she would be unreliable, and I would need to drive this fight.

So I have, pushed the entire treatment process, advocating for my dad. Researching facilities/mesothelioma treatment leaders, setting appointments, chasing pathology departments for slides, watching/listening to medical conferences and reading clinical whitepapers in the office. We decided on Mount Sinai in NYC. I have been at every appointment, every follow up, I read every word on every report. I am the first phone call if there is any occurrence, if my dad can't find a pharmacy with extended release morphine, if he is having trouble getting an appointment, if he needs scans scheduled, or slides cut from his original tumor.

My mom is a cloud of unproductive hysteria and I do not blame her, I acknowledge the difference between a husband/wife relationship and a parent/child relationship. I acknowledge that I will never know what that feels like. Children are meant to bury their parents and carry on with their lives, but spouses who expected to have an entire lifetime but then receive a shock like this feel robbed, and they are right to feel that way. So I take her hysteria, her anger, her frustration and I try to convert it into something productive.

I'm trying to stop the rest of life happening. I'm trying to be unselfish. I live in NYC, I'm paying my bills, I'm working a high-stress job in finance. I help my kid sister with her college homework, her resume, serve as an emotional shield. I call home every day, I take the train back to central NJ every weekend to see my parents, do house work, cook and bake. I have days where I don't want to get up but I do because my dad's life depends on me staying productive. There was an incident last weekend where I was having difficulty with my little sister's attitude and my mom smacked me in the face, asking what was wrong with me and saying it was a disgrace to be arguing with my sister when my dad is sick, as though it were even possible for me to forget that had I wanted to. In her rage she told me not to come home, which destroyed me, but I had to immediately forgive her because I don't know how much time we have together as this family and I don't want to have any memories of things being less than wonderful.

It came to a head this week when I was calling and talking to UnitedHealthcare about whether immunotherapy treatment would be covered. We postponed the treatment appointment twice because the review process was dragging on. My mom asked for an update and I called home to give her the information. My dad picked up the phone mid-conversation and essentially told me that I was damaging his chances of getting approved, that I should just let the hospital staff handle it, that the doctor had said for lung cancer patients the immunotherapy drug rarely gets denied, and that I am not getting anywhere by calling or emailing or chatting and that I'm just needlessly irritating people. 

I don't need anyone to tell me I'm doing a good job, or an ok job. I don't even care if someone tells me I'm doing a bad job. All I need is, for the person that I'm doing all of this for, to NOT tell me that I could be doing a better job. And because I'm so hyperaware of time and how little time might be left, I have to force myself to immediately let go of any feelings I have of anger or frustration or negativity and just keep going. Because these doctors and nurses and insurance staff see people dying all the time, they have to be numb to it. But I only have one dad, the man I adore most on this earth, so I have to muster up all the productive neuroses I have to make things happen.

I am exhausted. I feel empty and depressed and alone. I want not to go home this weekend but I found out from insurance that the immunotherapy treatment was denied, so my mom wants me to go home so we can discuss next steps. I don't even know what to do. I just think I'm losing my mind.