Crappy air tools are simply less efficient than the good ones.
CENTRAL PNEUMATIC ITEM # 94802
Maximum Torque 230 ft-lb
BPM 1089
Air Consumption 7 SCFM
Ingersol-Rand 2135TIMAX
Maximum Torque 780 ft-lb
BPM 1250
Air Consumption 5 SCFM
Most 1/2" gun I've seen are around 4-5 CFM.
You're running a Viair 450C continuous duty - 2.5 gal tank, outlet at front bumper. You're compressor is rated for con't duty but it just can't keep up. At 90 psi (recommended psi for air tools) you're compressor will pump out only 0.97 CFM.
You've only got a 2.5 gallon tank so you'll be emptying it in a hurry and it will take about 30 seconds for the compressor to got from 85 To 105 PSI.
You may be able to get one lug-nut off at a time, wait 30 seconds for the compressor to fill up, then another. All things being equal, it may be faster to just use a ratchet.
If you really really don't want to spin the bolt by hand then get an electric impact and carry 2 batteries. (They will run a while on a charge and if you've got an inverter you should be able to charge in 15-20 mins).
Milwaukee 2663-22
Maximum Torque 450 ft-lb