since I drove it with the donut. (maybe 75 miles, under 50 mph
this, by itself should not cause a problem.
not an ideal situation,
but not a trans killer either.
the flashing AT Temp light indicates that there was an electrical fault in the trans the last time you drove the car.
given your symptoms,
it is caused by the duty C solenoid that controls the transfer clutch in the rear extension housing.
there is a possibility that several, three, drain and fills of fresh ATF will improve the situation.
the duty c could be stuck.
but even if the duty c has to be replaced ,
it is not a terrible repair.
$100 parts, several hours in labor,
some new ATF.
TCU = trans control unit, (computer).
don't bother checking the ground,
that is not the problem.
change the fluid,
do 3 drain and fills, (just like engine oil)
with driving in between.
then give it a couple of days to see if it improves.
if you do not want to , or can not afford to replace the duty c,
assuming that is what is needed,
you can remove the rear section of the drive shaft and make the car FWD all the time.
i did this for 40k miles with my 95.
it ran great.