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You are being modest, but your questions betray thoughtful knowledge of these topics.
Briefly, Edwin Hubble's 100 year old expanding space model (sometimes called Hubble Flow) has been unprovable by any observational standard. Frankly, his theory was meant to explain the possibility of a dynamic but eternal universe. Einstein was having a similar existential crisis noting that the universe had to be changing but did not believe in an origin.
On your point regarding the CMB, this was observed after their deaths and implied a momentary origin to standard model particles in the universe. Ironically, Einstein and Hubble would be spinning in their graves to know their theories are now conflated with a cosmic origin theory. But other evidences like the average distance to most standard quasars being 10 BLY and the concept of entropy itself favors a finite universe. There are those that still argue an eternal universe much as we know it now, but that is a minority poisition.
Rgearding redshift, Hubble's theory assumes we are in such an eternal universe with a yet unprovable exotic change in metric. No one currently believes both of those things to be true. There are many theories to try and explain redshift either as a bandaid to Hubble Flow or proposing their own yet unproven or exotic property of the universe.
I have one such theory that appears to have not been considered by anyone, yet contains no exotic metric, change in known physics, or unknown particle. The only prerequisite my theory has is that the standard model particles of the universe must have had a relatively simultaneous origin. Otherwise, I expect it is what Einstein's Cosmological Constat would have show if he was willing to think beyond his personal beliefs. You can read about it here:
Finally, I agree that all energy and matter appear to be eternal. However, the form that matter/energy takes can change or is a more complex relationship than we currently understand. The current Higgs theory is that the fundamental particles/forces of the univere may have come from the decay/state collapse of a particle of immense energy that violates Planck metrics of the standard model.
It is my belief that the universe (regardless its manifold, metric, etc) could have been full of entangled Higgs-type particles. Since quantum entanglements apprears to allow for simultaneous state collapse of multiple particles at extreme distances, it seems reasonable to me that a pre-standard model particle universe may have existed and state collapsed into the standard model particles we have now. Same energy, different particle forms of it.
I don't know if space is even a thing, and what we call time is simply our relative rate of c which our ability to observe and interact is tied to. Both concepts are difficult to define and very dependent on ones model of the universe.
To be sure, we have limited knowledge and can only observe the univere from our point of view. No one can say for certain they have the accurate answer, so it is important that we are open to considering any ideas that have not been fully explored while being critical of all theories, especially when evidence is to the contrary.
