1991 caprice with 305 throttle body, bit of a unique help request because i'm disabled, lack the money for a mechanic, and have to get to medical treatment so need hopefully something simple within my abilities to get running again.

My mechanical knowledge is splotchy/self taught only and my confidence low - I successfully swapped a clutch on a saturn SL, but failed rebuilding a carburetor for a lawnmower which never ran again, so apologies if i'm slow or unexperienced at knowing what to do or how properly.
Had to have this parked (due to low mpg) for the last year or plus, I put Pri-G in the tank so wasn't too concerned, had a half or 3/4 tank (not sure how accurate gauge is) or so when I did.
Had my saturn car break down so suddenly needed to use this/the backup. Didn't start instantly due to sticky residue in TBI, I sprayed carb cleaner (yes carb cleaner, only thing I had handy and couldn't get proper TBI cleaner without a running car) onto it which both cleaned up the spray near instantly and worked as starting ether - idled perfectly smooth with no misses or problems. Drove to the gas station and put on 3 gallons gas to mix out some of whats already in there.
Drove 60 miles around town with absolutely no trouble the last two days, have been expecting no trouble.
Suddenly went to crap out of the blue when pulling into a parking lot - died on me, on restart it ran HORRIBLE, missing so bad I could barely keep it running no matter what I did with the throttle, accelerating any near impossible, but would maintain jerky speed once I was there. Stopping at a stop sign or light would have it die every time.
I immediately filled the tank at the nearest gas station to dillute out what was left, putting in about 7 gallons, then struggled to start the car and limp it home which was 5 miles away.
I put 2/3 of a container of fuel injector cleaner into the tank (all I had left) and probably a triple dose of Pri-G (which unlike Stabil can be used to revitalize old gas, and yes it works, quite amazingly even) into the tank, but could only stick about a liter of additional gas into the tank to try mix any of it. If i'd had the Pri-G with when filling at the gas station it would work better i'm sure.
Tried to start it again today, it will start but immediately dies without abusing the throttle. Tried to run a few minutes to get what I thought was bad gas through it but it still runs bad. Worked the throttle body with some carb cleaner on a toothbrush assuming maybe the spray was just cloggy like when it first started - this noticibly improved the spray pattern but it runs just as bad so maybe it's the gas..?
I'm aware I need to give the Pri-G 24 hours or so usually and don't know how well it will be mixed under the circumstances, but other than sitting and waiting (as i'm needing to get to medical treatment 250 miles from here as soon as possible) and hoping it starts better later I need to look at other strategies...
Not sure how hard it is to replace a TBI but that assumes that's even the problem and dunno if a junkyard part run any better from sitting, A-graded or not. I'm hoping the mix of Pri-G and 11 gallons fresh gas by now (which should have mixed with what was maybe 15 gallons older gas) will take effect, and i'd assume anything nasty would have been caught by the fuel filter... and if that were clogged i'd assume it might idle okay but have problems maintaining a higher rpm, when it's more the opposite. Obviously pretty sure my ignition is fine when it ran the first 60 miles fine.
Open to suggestions.
