1. 134a NOT Freon:@
2. 134a will still bubble in the sight glass.
3. Unless you had a catastrophic loss of coolant, if you just had a slow leak, then you NEVER add Oil at all. The ONLY correct way to add oil is to pull the compressor, drain it and add the correct amount of oil per the compressor. Adding oil when not required will add too much oil to the system and degrade the cooling capacity.
4. The Charge for a Ford Class A chassis is dependent on the complete system. The range is 2.25 oz to 2.75 MAX oz. Doug
PS, you added 1 can too many---TOO MUCH 134a will not cool as the correct amount. There is a curve----Once the 134a reaches its correct amount, adding too much starts a lack of cooling and the output temp starts to raise.