Pull out the blower motor assembly along with the wheel and clean it as well as cleaning the housing out...........
Worn serpentine belt? Bad bearing in belt driven accessory; alternator, idler pulley, a/c compressor etc.
im sorry about your luck you should NEVER use any type of flush on a high mileage there are deposites that imbed in the soft metal bearings and those deposites are helping to keep the motor tight when you use a flush it washes away the deposites and now the motor is loose and needs a bottom end rebuild the los of the oil pressure gauge is most likely due to main bearings