Unfortunately, I don't think there is a hard and fast answer to this.
My mom is one of three girls, and when Gram had her stroke (Gramps died 11 years earlier), between my mom, my aunts, and me, there were only 3 evenings across the three months until she passed, when no one could be at the hospital, and we all felt horribly guilty about it.
Fast forward 10+ years, and my mom had both knees replaced (at the same time, by choice) and was in the hospital and rehab for ~3 weeks). Aside from the actual day of surgery, my dad went almost every day and I went every other day. My dad and I both had to work, so we called when we could during the day and headed over there in the evenings. But I am a single mom with a young daughter, and it just wasn't feasible to be there every evening or to have a sitter multiple times a week.
Two weeks ago my mom fainted at work and needed 8 staples in her scalp and an overnight stay for testing. Thankfully, everything came back normal, but it was tough. Someone had to get my daughter from her afterschool program and both my aunts had full agendas. I left work early, my dad came directly after work, but then left to get my daughter.
We needed to retrieve my mom's car, so I had to leave shortly after my mom got settled in her room to get my daughter home for homework, shower and bedtime on a school night and to free my dad and aunt to get her car.
Now, I will say that it sounds like your dad is more dependent on your mom than my mom is on any of us (she is younger - 69).
The hard answer is that you still have to live you life - you still have to grocery shop, attend school functions, deliver and pick up your kids for activities, work, etc. etc. All of the quality hospitals in our city at 30-45 minutes with no traffic.
I fear for a time when my mom might have a stroke or something and being an only child, trying to balance visiting and living. Since you have siblings, you can divide and conquer. If someone can distract your mom for a day, that would be helpful to her too.
It might also be time for you and your siblings to step in with some tough love, which is really hard when the tables are turned and you need to direct it to your parent.
No easy answers, unfortunately, but hope this helps a bit. Saying a prayer that he is up and about soon and that you find some peace with managing all of this. No fun being in the sandwich generation.