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.