I just looked up the pressure v. temperature for Freon 22. At 250 psi gage pressure the temperature in the condenser should be about 112 F and at 65 psi gage pressure the temperature in the evaporator shuld be about 35 F. Both of these sound about right and you probably have enough Freon. AT 75 F and 80% the dew point is at 68 F so the AC would be pulling a lot of moisture out of the air. About the cycling, my guess is this, the control thermostat is pretty close to a vent and is subjected to the cold air from it. At 75 F it cools down quickly to your set point and shuts off. The humidity has little to do with it. At higher ambient temperatures, the vent air is a little warmer and takes longer for the thermostat to cool down.