FIRE with a dependent elderly parent? Need a “reality check”

[norisk]

I need a reality check on my plan.
My plan is this – I have a portfolio that would allow me to maintain the current level of expenses at about 5% withdrawal rate. I know 5% is quite high, especially in light of the recent discussion on the 4% thread, but I only need it to last 20 years because in 20 years I will get an employer paid pension (with COLA) that I anticipate will cover all my expenses at that time and for the rest of my life. So for 20 years 5% appears pretty safe (FIRECALC shows 92% success rate and the first failure doesn’t occur until year 16, by then I would likely have lower expenses – see below). Plus, if it really gets bad, I am not averse to picking up some part time work just to cover expenses for a year or two (I even think it would be fun to try different part time jobs, even not high paying ones).
Here is the problem. My mother is living with me and she is fully financially dependent on me (meaning she has no other income due to her being from a foreign country that does not have much in a way of SS). Also, because of her visa status she does not qualify for Medicaid or anything like that (although in 5-6 years I might be able to get her a green card and then she might qualify for some assistance). So I now pay for her private medical insurance (the price of which is included in my expenses above). This insurance has a 5k deductible and 10k maximum annual out of pocket.
She is 74 now and in relatively good health at the moment. I figure she could live until 90. I just run a detailed scientifically based life expectancy calculator for her that showed 87. BTW this might be useful for some of your planning - http://www.livingto100.com, it asks a lot of questions about health, lifestyle, diet, etc. So I think this is a fairly good estimate.
I need some “reality check” about my budget for her medical expenses.
I have a separate “bucket” of about 100K that is not included in my portfolio amount above. I wonder if this is enough to cover her medical expenses till the rest of her life (she has very little in a way of other expenses and those are included in my budget above). I am not the kind that would put her in a nursing home and as I expect to be retired, I would just care for her myself at my home (I am not averse to doing basic nursing staff either). Since her insurance has 10K maximum out of pocket, presumably this amount would last for at least 10 years at the maximum out of pocket expenses. The cost of insurance is covered in my own budget, but the problem is that it is raising every year and likely will raise much faster than inflation because of her age, but I have no idea how fast it will raise. At some point I might need to draw from this “bucket” for her medical insurance costs.
Is this all realistic?
Am I missing something important?
Norisk