Compressor - check my guestimates please!

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I picked up a compressor a few years ago and just now got it completely up and running. It's a wayne air compressor (that apparently hasn't been made in a few decades). It's got a 3HP motor on a 220V circuit @ 16A with a 2-stage compressor. There are two tanks that total about 80 gallons (a 30 on top of an 80). Based on the numbers from this page - http://www.truetex.com/aircompressors.htm - the compressor will output about 14CFM @ 90 PSI. Now, I know that you can't find any info anywhere about these compressors anywhere except that they were apparently a pretty good unit back in the day. I know that my grandpa used it for a couple decades in his shop and never lacked for air, but I don't think he ever did a lot of REALLY air intensive stuff.

My question is, do these figures make any sense at all to you guys? Do any of you have compressors like this? Also, what's the most air you've used for different air tools that you use? My understanding is that a die grinder is one of the biggest air hogs at around 15 CFM.

Also, the tank is rated for 200 psi, but it's my understanding that the compressor will last longer if you let it cut out at lower pressures. The original pressure gauge went to 200 psi, and it was swapped out for one that goes to 160psi. How do I adjust it to cut out at around 140-150 psi? I let it run today until it got up over 150 and it didn't shut off? It had the switch that has the two screws that either increase or decrease spring tension inside the unit. Do I increase or decrease the tension to lessen the pressure the compressor kicks out at? Any ideas on how a single turn effects the pressure?

Ok, so I know that's a lot of info! Thanks for all the help!