Channel
Address
Circuit

Channel is what you use to program the fixtures in the board, its the most arbitrary, dependent on the show.

Address is the DMX position in the chain to control the unit. 1 to 512

Circuit is what is used to identify physical wiring in a rack. If you have a 24 way dimmer rack, Circuit will be 1 to 24, and may include the name of the rack

Sometimes DMX Address is 1 to 1 with the Circuit of the rack.

In more complicated designs, the circuits have individual DMX addresses, to balance loads more efficiently, or group dimmer outputs in more logical patterns.

It depends on your rack whether you can only set a starting DMX Address, so the circuits have to be in direct DMX order; or if your circuits can have different DMX Addresses per Circuit.

A DMX Universe (1 DMX wire) holds 512 DMX channels, with each channel consisting of 255 steps. A lighting fixture can consist of multiple DMX channels, with the first channel being the fixture’s DMX address within those 512 DMX channels. A dimmer typically refers to the amount of light projected in terms of brightness, and often is set to a fader on a console. Faders can also consist of just about any scenes that the programer desires depending on the DMX software/hardware being used, so in short, it just really depends.

How to Program DMX lights – SCENES CHASES & BANKS w Rockville ROCKFORCE 192
https://www.youtube.com/watch?v=jFIKWoPcZGI

How to program DMX lights for beginners (simple lesson)
https://www.youtube.com/watch?v=dJQAZsNwcv4

Yes.

“Regular mic cable has basically no insulation and DMX is very susceptible to interference….”

I have to disagree somewhat with this. Normal mic cables have typically quite good insulation and good shielding – in many ways ok for DMX.
The most serious problems are typically related to wrong cable impedance (causes signal attenuation and bit errors on long runs). Sometimes the cable insulation materials can cause extra signal attenuation. And ground loops can cause issues.