I am flummoxed about the entire thing.
Is there scientific consensus on dark matter and energy?
No.
Is there scientific consensus on the universe’s limit or infinity?
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Yes, that it can not be infinite, that it began.**
If we have not discovered the limit of the universe, how can math handle such realities?
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Transfinite set theory deals with actual infinities, which, in reality, are absurd, as demonstrated by Hilbert’s Hotel. A poor analogy, but math, like philosophy, can deal with moves three steps ahead of empirical science.**
Is it possible to see light from a scource 50 billion years away? Or how far can we see the light from stars and galaxies?
No. We can see 13.7GLy in every direction.
Are there different scientific parties on these issues, like Democrates and Republican. The Republican say that they are correct and the Democrates say they are correct.
Not really - it’s much more multifaceted and less partisan.
Can human reason accurately discern answers to these things?
Unaided? In many cases, yes (Aristotle, by pure logic, deduced that the Universe must have a beginning, over 2200 years before empirical science demonstrated it: most scientists held to a steady state theory - in contravention of the metaphysical evidence - before that point).
It seems to my intuition that if there is actually dark matter and energy, the entire Big Bang has to be renamed. It would radically change the theory.
No, it wouldn’t. It may change the result, but it does not change the actual event, nor following events on the scale of the Planck time, nor the fine-tuning thereof: the “stuff” or equations itself remains unchanged, but some variables and eigenvectors would not be.
Are the Big Bang scientists creating beings of reason and then trying to explain how these beings of reason could actually exist?
If I interpret you correctly, no - most actively try to disprove the need of any creator, and have gone to absurd lengths (e.g. chaotic inflationary multiverse hypothesis) to try to keep any Theistic foot from getting in the door.
Well, I am not sure if I am clearly stating my confusion or not. But I am truly beginning to wonder: Yes, Virginia There Is a Big Bang. And Dorothy, “do not pay any attention to the man behind the curtain.”
The Big Bang is the best empirical/scientific evidence for God’s existence and providence of any yet discovered. It’s not as good as the metaphysical evidence, but in some places it reinforces it.