A/C failure after enging install

I just recently installed a engine in my Impreza. This A/C was working fine before I started. During the enging removal, I unbolted the compressor as well as disconnected any wires and simply pulled the compressor over to the side to complete the engine. In order to make enough room for the work I had to tip the compressor almost upside down. with the lines attached . It stayed this way for a few days.
After installing the new engine i bolted up the compressor to it previous position. Shortly after that I could hear a hiss from the rear high side hose that connects to the rear of the compressor. It was clear that the o ring seal had failed due to my over stressing this connection. After replacing the o ring and letting this system sit on a vacuum for well over an hour I verified that no leak was present.
I added the recommended amount of 134a per the specification sticker under the hood.
What I dont understand is the low side readings are anywhere between 8 - 10 psi ( entirely to low ) and a high side reading of 250 psi.
I know this system has the right amount of refrigerant but the low side readings are to low and no cool air.
Also when I test drove the vehicle I had turned on the A/C and as I accelerated I could hear a fast loud hiss of pressure being released.
Could you please point me in the right direction to fix this ?

Any help would be great.

Thanks