Soldering vs. Brazing

"I cannot find a recommended air pressure for copper tubing, but 175 psi sounds like a bit beyond what would be recommended."

The rated pressure for 3/4" Type M Annealed is 346 psi at 150F and the burst pressure is about 2350 psi. Type L has a working pressure of 495 psi.

The pressure rating of 3/4" joints with 95/5 tin/antimony solder is 1000 psi, but the rating for 50/50 tin/lead is only 200 psi, so tin/antimony is the best choice for high pressure.

Those pads are probably only sold by real air compressor shops, at least that's where I found mine. You don't need to anchor the compressor to the floor, it won't walk when it's placed on those pads. They're only about 1/4" thick, but they certainly work. Also, you are talking about 175 psi? That's higher than you will need and will put a bit more stress on the system and your tools. I think 125 psi is a more realistic pressure.

You are probably correct. I called Ingersoll-Rand today for some info on impact wrenches. They say that their wrenches are to operate AT 90 psi, so I would need to down-regulate prior to the tool. I was planning on that downregulation being at the point-of-use, however, and not at the compressor outlet prior to the copper plumbing. That is what a few diagrams I had come upon had shown as well.