First answering your questions:
1. You can compress them with a c-clamp just make sure to use the old pad to push on, sometimes I have just used hand pressure. Open the bleed screw and bleed the brakes after doing the brakes.
2. Replacing the fluid by syringing out the master is probably good enoughfor maintenance, however bleeding the lines is the only way to get all of the fluid out. If you are doing the front pads you might as well flush the lines.
3. Replacing the fluid like the dealer did is good enough for maintenance, but if you are doing the pads you will flush the lines out anyway.
The dealer saying it is problematic to get air out of the lines while flushing is BS. You are pushing fluid through the lines, not air. And if that was the case how could you ever change a caliper? It is just easier and cheaper to do it that way - kind of like changing the trans fluid and not removing the converter, it is not worth dropping the trans to get every drop out during maintence, get most of it and call it good enough.
Our brake fluid is hygroscopic, meaning it takes on water (so your brake components don't rust from the inside out). Replacing your fluid is done to remove the fluid that has taken on water, and to allow future capacity for holding water. Changing the Master will eventually work its way toward that end, just not 100%. But particles other than water tend to stay deeper in the system.
I have heard of several people with ABS problems after compressing the calipers without opening the bleed screw. Changing the master fluid right before doing the brakes and compressing the caliper without opening the bleed screw will still push the crud in the line back through the abs unit. Solids settle to the lowest elevation, any rust and stuff will settle to the calipers, only flushing will take that away.
