A & C
I think you are splitting hairs. At FNC and CMF you ARE following the missed approach for the runway that you did the approach to. As you point out, it's just using common sense for the first bit to establish safely on that missed approach. Done both.
The rule is as already stated by many; follow the missed approach for the instrument approach you flew. Oh, but let's add the little caveat that DON'T compromise the safety of the aircraft whilst establishing yourself back on that procedure.
What works best is to fully brief the G/A actions at various stages of the circling manoeuvre to ensure, as ever, that you are both singing from the same song sheet before you get there.
PP
Edited to add, what are your thoughts about ILS 18 at Chambery in the dark and followed by a G/A? Interesting when they have another aircraft following you down the ILS eh?