[JayG]

A good alternate method with a power bleeder is to do it dry.
Don t put fluid in the bleeder, fill the reservoir with fluid and use the bleeder only for pressure
Just be sure to check to make sure there is still fluid in the reservoir.

Bleed the rear brakes even if you are not changing the pads

bleeding only uses a few ounces of fluid. Bleeding is only removing the fluid in the caliper and maybe a little more as well as looking for air bubbles

If you are removing most of the fluid in the reservoir, and replacing it and more with fresh fluid you are flushing the system, not bleeding it.

As to as how much fluid should be in the reservoir after you are done.

First change the pads, then bleed or flush the system.
When you are done with that, fill it to the MAX line

bleeding/flushing is the last thing you do