Who are "objectivists" and where do they claim that "objective evidence (valid evidence is usually objective) can do everything"? What is the "everything"?
Who is GIGO, a pimp?
Knowledge is limited by numerous things, like facts, data, instruments, and time.
You surely mean the fictional version of the Abrahamic "all-knowing God" since no gods are known to exist, nor any of their properties known as an obvious fact, yes?
Given your uncertainty of everything I would expect your treatment of God (as a concept since there is no evidence to work with) would be two tiers down. Even if there was evidence for any God you would have doubts, yet given there is no valid evidence for any of the many god concepts your natural skepticism would render it even less likely than the average atheist does.
GIGO you can google that.
Now for "I know" here is an example involving logic and skepticism.
It is semi-formal for a claim like say the cat is multicolored and not monocolored
Person one: I know that X is Y and not Z
Person two: I know that X is Z and not Y
First it is general and not just about religion. Secondly there are 3 possible outcomes. Two for respectively one is right and the other is wrong and one for they are both wrong because it is unknowable. Thirdly at least one of the two doesn't know, yet it doesn't follow that the person will die because of this or even have a horrible life.
So I wondered about this and checked the different versions of skepticism and figured out that I didn't have to know anything. I just have to have a set of beliefs, which apparently works for me and to me that is what I mean by to know.
So for knowing what the real world as independent of my mind is, I don't know that. I don't even know the probability of being a Boltzmann Brain or not. But since you know that, I would like evidence for that.
So since you know what knowledge is and are a scientist, you can explain the difference between methodological and philosophical naturalism and how come is that the former is based on unproveable axiomatic assumptions and not knowledge. And the latter is not science, but philosophy.
As for God, not all versions are religious. Some are philosophical and sometimes used as a theoretical placeholder for testing something.
If I know something, then what would it take not just to know something, but know all of the universe or even everything?
In that tradition God is simply the placeholder for all X in some sense.
So I am not a theist, I am even as religious and a deist not supernatural in the standard sense. I am philosophical and use God as a placeholder for the beliefs that the universe is fair, real, orderly and knowable. But since those 4 properties are not physical, but rather ontologically a case of idealism, I am religious and the universe is a case of ontological idealism and thus in a sense a God.