I once bought a 44 gallon drum of 'super' (leaded fuel) which had sat for 30 years. Got it for $20 LMAO. I used all but the last few litres of gunk in the bottom of the drum. Mixed 50/50 with some fresh fuel it worked good enough for an everyday driver.
The worst issue with stale fuel is the lighter liquid evaporates over time and leaves a greasy
oil like soup which can block jets and accelerator pumps etc. I imagine EFI injectors wouldn't be real happy running in soup and may clog shut even.
If I was in your situation I wouldn't be dropping the tank, I would be looking at cleaning the fuel rail out and maybe get a quick injector test at a workshop.
Naturally the octane rating of the fuel would deplete over time but this would be noticeable when you drove it hard. Since you aint driving start at the rail and injectors.
BTW, when fuel dries in a filter it can sometimes make it impossible for the filter to flow fuel.
Good luck