DO NOT allow the leak stop product to be used, even if your equipment is older than the universe. The service tech who ultimately will need to remove refrigerant from your system when it dies will hate every last drop of that leak stop as it fouls his recovery machine.
You probably have a leak, and it may be in the evaporator. Current R22 refrigerant prices do not make "gas and go" a cheap alternative to fixing leaks anymore, but a leaking evaporator is a losing proposition to leak fix when it is old. You may have to bite the bullet for new equipment.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.