Interesting! Close-up's of the tire fittings please? And/Or part numbers?

 

Most tire shops will take out the schrader as part of the tire install process. Inflate above the rated sidewall psi then let air out as they install the schrader.

 

You state that your compressor tank is kept between 135-150 psi, which is pretty typical. Almost all compressors also have a pressure regulator that sets the pressure into the hose. If you set your regulator to 80 psi, it will take much longer to inflate your tires than if you set the regulator to a higher pressure, like 100-120 psi. As others have stated, upgrading to a larger diameter hose will dramatically increase your airflow. Going to a 3/8" hose instead of the 1/4" hose will likely come close to doubling your air flow rate. Your compressor is plenty large enough to keep up with inflating your tires and really shouldn't be the limiting factor in this situation.

 

You might burn up the motor on your current compressor but if I were you I would add aux. air tanks to your compressor. Go buy 2 of those portable air tanks, connect them to your existing compressor so you have 3 reservoir tanks, this triples your available air.

Most buds of mine just use the tank from an old hot water heater but could be unsafe if you don't know what to watch for.

 

Another thing to think about is that the quicker you fill the tires, the hotter the air in the tire from compressing the air already in there. PV=nrT As it cools off, the tire pressure will lower and you should check and refill a second time. Slow and steady will actually win this race.