When Newton propounded his gravitational theory to explain the observed motion of the planets and their satellites, he did not (have to) start out with some 'preamble' explaining the origins of the universe, the solar system, or even the planets and moons. His theory was an 'B to Z', or more correctly, an 'L to P' type of explanation, and still has proved very powerful and accurate in explaining exactly what it set out to explain. Newton did not have to posit whether time or space were finite or infinite in extent. That didn't enter into the description. That his theories of gravity and mechanics happen to contradict a literal interpretation of the bible is the bible literalists' problem, not Newton's.
And so it is with all theories that we have to date. Quantum field theory assumes the standard model with the existence of certain particles and their properties. It does not (yet) have an explanation for why those particular particles and properties are the ones observed. And yet, it is able to predict and accurately describe a cornucopia of observed phenomena and support many massive technological industries, including the one that produced the computer on which you write your nonsensical posts.
Darwin's ToE accomplishes exactly what it sets out to do, explaining the mechanism for the origin of species starting out with the earliest and simplest life forms. It's validity is in no way predicated on its explaining the processes that led up to the conditions that produced that (or those) earliest life forms. Questions concerning the spacial or temporal extent of the universe, other than the need for an energy source and sufficient time for his evolutionary mechanism to occur, do not enter in any way into his theory or its fabulous success in explaining so much that is observed in the biological sciences. And, yes, Darwin's theory, as do all theories of biological evolution, contradicts the genesis account of the origin of species: that all species were created independently and within a single week.