Put your money into an HSA rather than an FSA. It's a free extra retirement account.
You don't need to worry about being locked out of your 401K after being sacked. It's still your money and they have to give you access to it, even after you're sacked. Transfer the money out to a separate 401K account that only you control after you've left the company. (Or don't, because I'm pretty sure they have to keep your account open indefinitely, but IANAL so ask a professional)
You should practice interviewing well before your last day. Interview somewhere you'd like to work at least every 6 months. Tell them you're not looking to move right away but you're curious about their company and team an open to hearing about new opportunities. Keep in contact afterward.
Not mentioned there, but commuter benefits cards have an expiration after which you can't spend the money, so make sure if you have a balance that you spend it before it expires. I once built up $250 on a card and forgot about it.