Micro vs. Macro-evolution -- an argument for those unwilling to accept definitions. All evolution is micro, but it is as inexorable as erosion. You seem to think that "micro evolution" is like some editor tweaking a submission. A bit of spelling correction here, and deleting a superfluous adjective there, and voila! the work is complete!
The work is never complete. We are all too wearily aware that evolution occurs because of random events. Let us surmise that an isolated species has had more than enough minor changes to exceed any definition of micro, and yet it may or may not be a new species. What defines whether it is or not?
Generally, it is accepted that it would be a new species if it cannot successfully interbreed with other species. Then it is necessarily on its own, to prosper or perish, as fortune determines. Eventually, it may go on to parent yet more divisions, more species. Or it may simply end like the dodo.
Such isolations can occur in just a few generations, or over thousands and thousands of years. The problem is, micro just doesn't know when to stop.
"a single common ancestor" -- Well, if you think multiple origin makes more sense, you can go with that. Some forest fires have multiple points of ignition, caused by lightning strikes. And many earthquakes are preceded by "micro-quakes".
Life is pretty diverse, but not quite so diverse that some relationship seems unlikely. The discovery and analysis of DNA gave us the opportunity to see whether, and to what degree, we are all related. Not just speculation, but chemical results. And guess what? We're all related.
"that single ancestor must have sprang from inorganic matter by some kind of chance" -- Here you are entirely correct. This is neither testable nor deducible. What will we conclude if we find life existing on other worlds?
"where matter/energy/stuff itself came from" -- What good is time and space? If you had the ability to create time and space, what could you use it for? Maybe it's just an arbitrary, random event, like the dance of dust motes in sunlight.
"the Big Bang theory which suggests that the universe has not simply always existed--a notion which if accepted forces a reasonable man to reject naturalism."
The Big Bang Theory comes out of simple forensic analysis. When it was deduced that galaxies were moving apart from each other, it became a natural mental exercise to wonder what it would look like to reverse the action. Reversing the action makes it look as though there was a tremendous explosion about thirteen billion years ago.
But I cannot infer a reason that a man should reject naturalism, or even alcoholism, simply because the Universe has not always existed. Who gives a snap what was happening thirteen billion years ago?
Prior to the Big Bang theory, naturalists viewed the universe as simply eternal. They would not allow for a beginning because that would mean defending the notion that stuff could simply come from from nothing.
Along came observations that the universe seemed to have a definitive beginning. If this is correct then there seems to be some less desirable more speculative positions naturalism must retreat to:
a) That stuff really can just pop out of nothing...and yet not do to any magic or super natural influence.
b) That the Big Bang is just a cycle in an eternal universe, that may have collapsed into itself.
c) That the "universe" is really a part of a larger natural world (or "cosmos") which is eternal, from which the universe sprang as a subset.
None of these positions is particularly attractive, but I think the least "fantastic" and most attractive to a naturalist would be "b". And on that point, I understand that the physicists do not think that the universe is going to collapse, but its just a one way ride to heat death...if this is so science is sending even more rain on naturalisms parade.
Last I heard, the naturalists in physics were all about multi-universe cosmos theories, so I guess the option "c" is the latest rationalization. The interesting, and actually entertaining to us non-naturalist part about this is that they have to presume an infinite number of these universes in order to make the systems they invent eternal.
The motion of dust in sunlight is fairly arbitrary. Just as an important difficult decision a man makes after careful consideration and reflection is deliberate...but wait...along comes naturalism...and sorry I guess we must conclude they are both just arbitrary and random...as is everything else such as reason and morality.
Sorry, naturalism asks me to conclude too many idiotic things, so I can't accept it.