Quick n' easy check:
Make sure your radiator and A/C fans are turning the correct direction. This may sound silly, but it's happened before.
Another check:
When the A/C is running, from inside the engine compartment, find the inlet/outlet to the evaporator. Carefully touch the input line (small) and the output line (large) with your finger. Beware that they may be very hot or cold. Also keep your pressure gauge hooked up so you can note the pressure.
This should help you establish a few things. The small line should be ambient temp, or slight warm. The big line should be much cooler than ambient, or straight up cold.
If the inlet line is HOT, and the outlet is cooler, but not cold, your condenser is not rejecting enough heat. I.e. It's dirty, fans aren't doing something correctly, etc etc.
If the inlet line and the outlet line are the same temp, something is wrong with your expansion valve. Considering your pressure readings, this is unlikely. However, if the inlet and outlet are the same temp, you are probably not getting a pressure drop via the expansion valve. Since your gauges are registering a pressure difference, this would mean you have blockage of some kind between the high side pressure connection, and the evaporator inlet.
If the inlet line is ambient temp or less, and the outlet line is *really* cold, you are not removing enough heat from the cabin. I.E. not enough air is flowing over the evaporator due to a bad blower, air leak, clogging of the exterior, etc.
Another check:
Did you confirm the cold/heat blend door in the large HVAC box after the evaporator is completely blocking off the heater? I would try to visually confirm the lever is moving through its whole range.
If ALL the above stuff seems to check out, I would do this last measure:
You could 100% confirm the heater core is not contributing to temperatures by disconnecting the coolant lines to the core, and looping them.
