Indeed. Good grief. Did you even check out just the two links I posted? At the very least?

: No. The Big Bang Theory was developed to explain the observations: chiefly
: the microwave background radiation and the observation that objects are
: more red shifted the further they are from the observer.

That's exactly what I said. It is one explanation developed to best explain what we observe. An explanation for a proposed event that took place in the past, which is neither observable nor repeatable, let alone testable. Many adhere to that theory as the only plausible theory of the original of the universe as we know it.
If someone were to present some other origin of the universe, in any fashion, that did not include the Big Bang, would you listen? Or would you dismiss it? If the latter, then your default stance is that the Big Bang happened, and no one can postulate otherwise. That's dogmatic assertion of an unprovable axiom.

: All observations are interpreted - your brain forms impressions of the world
: by interpreting sensory inputs. All observations are indirect.

I'm not going to get into a philosophical debate about what we can rightly consider "observed". You and I have an understand of what we see. We consider it observed because everyone shares the same experience, and it's a matter of practicality. You are avoiding the point: What we have not observed - to the degree of experimentation and observation with our own eyes and experiences - we can only attempt to explain by forming a theory utilizing what we have observed.

: To get back on track - you have claimed that all life comes from life. I have
: pointed out that the universe started off sterile.

How do you know? (not how do you postulate) How do you know the universe started off sterile? Answer that, or we are done.

: There was no matter in
: the beginning never mind assemblages of matter big enough to constitutes
: biological organisms.
: Please address that point.

I have. Repeatedly.

How do you know? You were NOT there to observe it. How do you know that there was no matter in the beginning? You are ONLY able to form explanations which you feel are best supported by observations made here and now, to this date. Do you deny that?
Regardless, when it may have happened is of zero practical relevance, if it cannot be tested.

Be a good scientist, think critically: TEST your postulation that biological life can arise from non-biological matter.
Demonstrate that biological life can and does come from non-biological matter, with zero biological influence. Do it. Or point to someone who did, and has sufficiently documented the evidence and the experimentation process. If you cannot, then you have not addressed my point, and my case rests:

There is currently no demonstratable, observable data that biological life either has a "vital spark", OR that it can ever arise from non-biological matter.
The default stance is only what we know: We observe biological organisms, and we observe non-biological matter. There is a difference, and we do not (yet?) know how to cross that mysterious boundary that distinguishes non-biological matter from biological organisms.

That is the long and the short of it.