I Is the supply of the observable CMB radiation limited?

[PeterDonis]

In an infinite, non-expanding universe, if there was a starting CMB in blackbody and the photons were redshifted later by, for example, a tired-light mechanism, the blackbody nature of the CMB would not be able to maintain because there was no dilution of the photon density.

A "tired light" mechanism would not maintain the blackbody nature of the CMB even in an expanding universe. You have already given references that show that. The reason has nothing to do with "no dilution of the photon density"; it has to do with the fact that a "tired light" mechanism does not produce a redshift due to spacetime geometry and relative motion; it produces it by an interaction with intervening matter. That is why, every time I have said that a redshifted blackbody is still a blackbody, I have qualified it by saying that the redshift must be due to spacetime geometry and relative motion.

Your original question has been answered, repeatedly, and how redshifting of a blackbody works have been discussed in some detail. Enough is enough. Thread closed.