As you suspected, your low recent expenses make it difficult at first to see the reasons for continuing to work, especially at a job you dislike. But I understand the possibility that old age could be costlier once you lose some of your abilities; I agree that's worth planning for.
That you've set $800k financial assets as your benchmark for being prepared seems reasonable offhand. But whether you can safely quit now, should slog "full time" for years or should downshift your work could depend on various assumptions, so permit me to dig deeper.
You work for a govt agency, it sounds like. Most govt workers get some pension credits but those are absent from your description. Are you contract only, no pension credits? (I'm vested in 2 pension plans though with only small pension amounts; 50something, expenses 21k, several years FIREd; peer to peer questions here, maybe).
Have you prepared tentative withdrawal sequences for the 3 scenarios (quitting now, CoastFIREing, 3 more years)? If so, explaining them might help the reader assess.
Fwiw, I myself assume that old age will at some point require assistance, but that that phase will be finite. Also, I assume roughly the same cost regardless of whether my future disability (so to speak) occurs soon or far in the future. These assumptions are not guaranteed, of course. After helping my Dad's Alzheimer's I do trust the stats that most cases of assisted living last 1 to 4 years, not the rarer and scarier 10+ years, though of course those occur too. I assume that when things go bad, I'll spend down 200k or 300k but not go broke. This is partly influenced by our successful search for decent assisted living that cost 4k to 5k per month during dad's Alzheimer's, not the 10k of scary Costly Coast (West Coast, East Coast) examples that do happen too. If you can line up some young trusty friend who might help with the financial management / casework in the event of mental difficulty on your part, that would make you safer. In the 5% or so chance I'm wrong, of course, I get stuck with Medicare/ Medicaid financing and, given family history, a good shot at Alzheimer's. If I didn't have some family to intervene with respect to case management (responsible Sis, gruff but caring BIL) I'd be even more worried but still I gain peace now (no more work! pleasant life) in return for a bit of risk later. Where to draw the line is to some extent a matter of personal values and judgment, not just a financial calculation.
Intuitively your plan sounds quite safe, but intuitively, I suspect you'd also be all right if you quit now. That said, if you feel like a bad sequence of returns would significantly endanger your plan (in other words you're set on a bigger safety margin than I think is strictly needed), my guess is the next 2-3 years will deliver bad returns along with excellent buying opportunities. If this market timing guess is correct, sticking with the job you have until end 2025 or so would be better for establishing the safety you really are looking for. Steady work would be better than freelancing in the downturn case.
I say this assuming that you can stand to work that next 2 or 3 years at your current job but if you really can't, pull the plug. At some point, you need to shift to playing offense - deciding to live the life you want. Without that decision, no amount of money will make you free.
In the scenario of 2024 Means S--t Hits the Market Fan, you'll feel uncomfortable quitting in 2026 but I suspect you'd actually be quite safe, even without any pensions outside SS. Anyway, awaiting any replies you share.
