Heat-pump style AC is not putting out cool air

Your guy knew nothing! Or is trying to take advantage of you! A full recharge of your system would take 6 lbs 3 oz of r22. This is an obsolete refrigerant, yes it can still be purchased. But is expensive you do not fill by pressure alone! A few oz of r22 can provide much more than 70psi , to properly charge a system super heat and sub cooling is used these are the pressures and temps on the low and high sides or suction and high pressure lines of the system while measuring temps. At both locations 70 psi is meaningless by itself. Contact a reputable hvac company , they may try to sell you a new system but 3 lbs may also provide a full charge and give you another 5,6,7 years who knows but it is a small system and may be worth a recharge.