Well, I haven't got rotary-wing flying experience and/or any test pilot friends...
However, I've got some experience as a flight simulation developer (Rise of Flight title), creating aerodynamic models of aircraft, and I'm still not convinced ;)
1.I can think of at least one configuration where this would be a non-issue - two tanks ahead and behind the passenger cabin. This will negate all effects you describe - and, well, if this does not work, there are plenty of configurations to choose from. IIRC, F-16 has 4(!) internal fuel tanks - and no problems with balance.
2.What are the problems you're taking about? The aircraft basically resembles Mi-28 configuration, only with coax rotors - which does only improve things.
3.If what you describe was the case, you wouldn't be able to perform autorotation on any chopper - because the moment you raise the collective to give some AoA to blades (to "flare" or whatever it's called right before landing), the blades would be stalling instantly. Alas, that's not the case.
There is always some space for *temporarily* adding AoA while in correct autorotation - and while one rotor would be losing energy due to added AoA, another would make up for it due to having AoA decreased. And remember, they are connected through gearbox, so overall rotation speed would just stay approximately the same.
How do I know it? There's no decoupling of cyclic and pedals from blades angle when on autorotation in Ka-50. There are hydro-enhancers, but pedals are mechanically linked to the blades. Hence, you are always using it to change blades AoA even when not having power. And somehow, Ka-50 can perform autorotation in real life...