I believe all the moves will bounce in both cases. England and Russia are clearly even, and France's moves will be bounced by Russia's.

then Russian moves are used twice?

Imagine that A and B has the same power and they are fighting with each other. At the same time C is attacking A, I think A will lose the battle. Because he faces two attack.

two bounces confirmed

ZF, the key is that both Russia and France are fighting over Munich. But they are equal strength so neither succeeds in taking it.

In your more general example, B and C are both, not only attacking A, but attacking each other too since they are both competing with each other, not just A.

yep

think of
Eng:
A Mun - Kie
Rus:
A Kie - Mun
Fra:
A Bur - Mun

same result different reasoning - but again it could be resolved as Russia and France bounce in Munich, and since England is moving to Kiel with only strenght 1 he bounces off the Russia unit aswell (in each case one unit is used twice)

Alternatively
Rus:
A Kie - Mun, A Sil S A Kie - Mun
Eng:
A Mun - Kie, A Hol S A Mun - Kie
A Bur - Mun, A Tyr S A Bur - Mun
(with no french units)
now again munich bounces but england has defended munich with burgundy's attack, so he didn't need munich to be holding)