Dumb compressor mounting questions

Hello all- bought a bracket (which I'm extending with some simple welds) and wondering a few probably dumb things. This is on the passenger side near the firewall:

First, what is this circular thingy in the pic below which I flipped over to mount in the next hole over? Assuming it was ok to do that?

Second, where can I ground the compressor without running a wire all the way back to the battery? Nothing seems to conduct. Just scrape off paint?

Third and the dumbest question: how to get a ring on the battery clamp? It doesn't seem tall enough to take regular terminal rings? What's the best way to attach to it?
TIA!

 

1. That's an annunciator- for sounds like the door unlock beep(don't quote me on this, but it is just a noise box. Fine to move it.
2. Compressor is a high amp draw, you're already in the engine bay, ground it to the battery is probably the best option
3. Mount the ring terminal on A. The bolt holding the cable clamp to the battery, or B. To the bolt for the alternator cable.

 

Thank you!

 

Bolt for the alternator?

OP are you using that thread bolt on the fender as seen in your pic? If not, use that?

 

Poor description, I'll post a pic

 

It's the Security Alarm Horn.

 

better to create a buss near the battery …………………….running ALL ace$$ories from it

rather than to tap a POS+ or ground NEG

IF there are I$$ues U wont compromise the original wiring harne$$