All right. This is an interesting topic, but you wrote a lot to mull over and reply to.

So just for the very start.
>can a constitutional court be wrong about the Constitution?
>Does it have an absolute final say on the meaning of its words
>The obvious common sense answers are no and yes.
So "no" is reply to the first question, and "yes" is the reply to the second?
I think a constitutional court can be wrong about the constitution however this doesn't mean anything, their decisions will be followed.
A constitutional court consists several members, an issue gets in front of them and they have to decide if it is constitutional or not. Each member will have their own opinion, they can disagree, they could disagree in their reasoning or their formed opinion, or both then they have to form an opinion together what they can give it to the public together as an institution.

This is a sidetrack, but:
>citizen's gneeral duty to obey authority
I don't think this is true.
>channel his disagreement into legal methods to question and overturn authority
But this is the generally accepted way of doing and achieving stuff, yes.