Units in stoichiometry
The stoichiometric coefficients is something else than you suggest.
stoichiometric coefficients:
The number of molecules of a given component that participate in the reaction as written.
The indexes $x, y, z$ represent quantities of atoms in a compound. So they do not have any units.
@Q2 Do you know what are $c, M$ and $x$ in the equation? If you do, you can answer your question. If you do not, than you should find it out.