RPM and manifold pressure questions

[The Stalker]

Excuse my poor knowledge but I'm currently in the process of learning my way in CEM. I switched CEM on after almost 6 months of playing the game (Il-2 1946 4.09m) and learning to fly from scratch.

I did pretty well actually, from not being able to destroy a friendly bomber to having up to 5 dogfight wins per mission, so I felt ready for the next level.

The thing is, I'm having trouble understanding prop pitch, rpm and manifold pressure things. For example, I'm flying a He-111H6 bomber. I noticed that RPMs stay on combat setting (2600) from 60% to 110% throttle. That had me confused, because I figured that lowering the throttle should have an impact on rpm-s, but only the manifold pressure fell. And where does the prop pitch come into play here, since I learned that it is used to keep the engine in the powerband, but it's in the powerband by itself most of the time.
Can someone elaborate a bit, especially the purpose of prop pitch?

Also, how do I make my bomber squad wingmen drop their bombs at the same time as me when I'm doing level bombings? If I order an attack ground, they seem to just drop their bombs without aiming properly.

Thanks.