Add a little referigerent (without introducing air in to the system) and check if the pressure numbers rises or not, if they don't the TXV is bad.
Which car do you have?
How you initially charged the system?
Did you vaccum the system?
Drier/Receiver replaced or not?
What about the compressor oil? type and quantity
Did you flush the system and how?
As per your statement the low side (return) pipe was ice cold at 1500 RPM, then why don't you feel the cold air inside the cabin. Is there any issue with your blower motor or the evaporator coil is clogged. Do you live in a high humid area?