99Civic AC Woes

Hello, I've been having lots of trouble recently with the A/C on my 99 Civic EX.
The A/C has not blown particularly COLD in a long time. Earlier this
summer, I had problems with the temperature of the air cycling from the 80s to the 50s then back up to the 80s and then back down.
The dealership told me I had a bad compressor, and I should replace the compressor, clutch, coil. I bought the parts, along with a new dryer and had them installed by a trusted mechanic. He had some problems getting the refridgerant into the system, so it was only blowing in the 50s and 60s consistently.
I got an evacuation and recharge from the dealer this past weekend. Did it bright and early in the AM, and the A/C was blowing in the 40s on the way home. Still does blow in the 40s in the AM before the sun comes up.
But once the sun is up, I have real trouble. In the hot afternoon, the system struggles to get into the 60s. I've tried: -turning off the unit's air recirculation feature (when I first start the car, the internal temp is 120+. I'll use outside, cooler air to start off) -turning the blower fan off from full blast. Not sure why, but that helps it drop a few degrees if it blows slow.
I have a simple digital stick thermometer that I'm measuring with, I just stick it in the vent and it clips on like pen.
Anyone have any thoughts? I hate to just start replacing parts, but I'm sweating my butt off and need to get this taken care of.
Thanks for the advice.
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