I can answer a few of those questions:
2) Yes, you'll need a power amp to drive a cabinet with the KPA.
3) Master/rig volume: Consider your master volume, your main volume control. You want to set this to achieve the loudest signal you want, irrespective of profile, i.e. all profiles should be at this volume. Rig volume, on the other hand, only controls the volume of a single profile. Use rig volume to raise/lower the volume of an individual profile if it's not at the same level as other profiles, or you want to use the profile as a solo boosted tone or to play up an effect, etc.
4) There's no right and wrong way to the way you route the KPA's outputs. Splitting the stereo signal into left/right mono is fine. You could also record the signal as a single stereo sound. If you're into reamping, you could record just one mono signal and then feed it back into the Kemper to get a stereo sound or a mono sound that you'd record. No right and wrong to any of these methods. See what your needs are and route accordingly.
5) It might not necessarily sound the same if you switch the cabinet to bypassed. This is because the profiling process captures a portion of the cab characteristics as well. One good way to record just the head would be to run the signal through a DI box, thereby eliminating the cabinet in the process. This way, when you run the profile into a cabinet, you'll have more of the amp and less of the cab.
Couldn't understand Question 1, if it is a question at all and not just a statement. Might want to rephrase that. Cheers.