this might be stupid but ive seen it happen plenty of times. im sure you checked it but im throwing this out there anyways. your low side gage is not peircing the low side or very little. what makes me say that is when you add refrigerant your low side stays above 100psig so it looks like the pressure is not going anywhere also you mentioned the suction port is freezing sounds like the refrigerant is misting through the valve core slowly. causeing it to act as a metering device and getting really cold.