2010 Nissan Versa - AC Problems

[Antimony26]

My AC is not functioning correctly--for a while I thought it wasn't working at all, but clearly now I can tell it doesn't blow cold air when the car is at high speeds (above 50 MPH) but works fine at lower speeds, blowing quite chilly air. I had the windows tinted which helped a little, but today it's 95, and we drove to the beach--arrived dripping in sweat! The AC Compressor SOUNDS like it's working--it's not a quiet part so I can say that with substantial conviction. Husband charged the Freon end of last year, and it helped for a bit, but not anymore...should I try to charge gain? Where should I look next?

Trying my hardest to retain the love for my little car...but dripping sweat makes me want to trade her in