Unfortunately you've gone as far as you probably can, unless you buy a set of gauges and hook in to see what is going on in the system.
I just got done battling my wife's A/C. First the suction line was leaking behind the ABS module, replaced all those lines. Then shortly after the A/C compressor started to leak, replaced that and we have been good to go since.
I dropped some serious coin on tools but they have already paid for themselves when the A/C compressor dropped out (shop wanted 1,500 to replace). I did it myself for around 300.
Granted I just got done buying a set of gauges ($200), a vacuum pump (400) but now I can basically fix any car at my house.
Take it in, most shops will diagnose for free (note this is usually a visual only which you have already done) but to really know whats going on, they need to evacuate, pump down, charge with dye, hook in with gauges and then they can check the condition of the orfice tube, compressor and see if the evap or condensor are plugged.
Expect to pay around 200 for a full diagnose and then depending on what is wrong can be a cheap as 100 upwards to 2000 if the evaporator is plugged or leaking.
