2007 Ford Focus – AC Not Cooling Enough

I have a 2007 Focus that has working AC, but I think the vent temp is not cool enough. The AC does cool the interior, but I can tell when driving that the vent temp should be colder. I put a manifold gauge on the AC system to check the numbers:

Outside temp: 100 degrees F
Engine idle: 900 rpm
—–
STATIC READING/AC OFF
Low side reading: 97 psi
High side reading: 98 psi
—–
COLD ENGINE RUNNING
Low side reading: 42 psi
High side reading: 230 psi
Vent temp: 63 degrees F
—–
WARM ENGINE RUNNING
Low side reading: 48 psi
High side reading: 240 psi
Vent temp: 65 degrees F

I noticed that the high side gauge needle was fluttering quickly during the reading. Any ideas on how to get the vent temp colder? Thanks!