Sorry to hear about your mom :(
The answer to your question is "yes", you are FI. Do with it what you want, but you no longer need to work for money. A sabbatical seems like a good option if you can get it, then you can always change your mind if you want to go back to work later.
I would do the following:
1)Look on
here to see your SS benefits. Remember they will give you benefits amounts assuming you continue to work and earn your last years wage until payout. So use the tool on that site (or create a spreadsheet easily enough) to see what the benefit is if you stop earning.
2)Figure out the health insurance. Many on the forum are very fearful of losing the ACA. That may happen, but honestly, even if it does you dont have too many years until medicare. Plug your SS income into a historical simulator like
this. Then plug in a very bad case situation, like 12K a year in medical ins from 53-64 and see how it rolls out. I would guess you'll still be at or near 100%.
Edit: and just to be clear, at your spending levels, you can manufacture a MAGI that's very low. If ACA stays around look at
this, if not, many states will have "low income" help for insurance premiums, you may qualify for expanded Medicaid (if its in your state) as well. Just read up on Medicaid's rules for recapturing assets if you are concerned about an amount of legacy money after death before taking it. I highly doubt you'll get stuck with $1000 a mo premiums
3)If you truly dread going into your job do NOT waste a year living at your "expected" retirement expenses. The only thing that changed recently is housing, are you happy with your current housing? If yes, you know your expenses. Just double check to make sure you're not sugar coating anything.
4)If you are unsure of Asset Allocations and how to invest post work, do a little research. Make sure you are comfortable with the risk you are taking with your investments.
Just to reiterate, because you will get some conservative answers on here... If I were you and really disliked my job; I would complete 1-3 next week and request a sabbatical the following. If the boss says "no", they would get my notice. Work on number 4 as you digest the awesome feeling of FI. Please do not forget the little people and regal the forum with the exploits of your FI life. Congrats!