Check freon level again. It might have leaked between your last check up and that day. Do the FSR replacement yourself, it's easy, it's cheap +/- US$70 and you'll change it in the future anyway. I went through the same ordeal. Considering I'm from a tropical country and need an AC always, it was really a PITA.

Other things you might want to check:

1. Does your AUX Fan work? (The big electric fan in front) non functioning or irregular faulty AUX fan will damage the AC system because of heat. This will cause leakage in the aluminium tubes if there's too much heat in the system. This is caused by FSR and/or a defective AUX Fan.
2. Do you have warm air on the right and cold air on the left (or the reverse). This is caused by the FSR.
3. Is there strong air breeze coming out of your air vents or does it seem like there is an obstruction after a few minutes / hours of operation? - ice builds up in the evaporator and prevents air to go through your vents. This is caused by the faulty drier, FSR or dirty/faulty inside temp sensors (in front of the AC control panel).

I'm not an expert and not trying to be one but these are based on my recent experience. Hope this helps.