Your questions are examples of the god of the gaps.

https://en.wikipedia.org/wiki/God_of_the_gaps

God of the Gaps is when the explanation for "we don't know" is God, without any evidence.

If anything, my examples are counter to God of the Gaps.

I ask how a being can be omnipresent in a Universe this large without any physical evidence for it even being here.

If the answer is "we don't know" then that is the non-God of the Gaps reply.

Every sparrow. Or so the song goes. God has excellent vision, apparently. He can watch over everything all the time. No doubt he watched my neighbor's cat catching one of the many sparrows that shelter in the bushes in front of my house.

And never mind all the time it must take him to watch every adolescent boy sinning on a regular basis. It all goes in God's "permanent record," you know.

People believe that. It's amazing.

Also, I'm not sure what the concept of "conceivable" is for an omnipotent being. It's sorta a given that one cannot understand such an entity.

tell us exactly what he wants and demands of us.

But that's different than understanding it's full magnitude. Most folks don't know much about their cars, but they know how to drive them.

no mysteries. And with some study I could repair most things in it.

I don't think that is the analogy you were looking for.

any level of detail down to the metallurgy of each component and the detailed functioning of them all.

The two things are not even comparable.

According to believers, all of them, and don't give me that broad brush bs, I mean every single one who believes god is omnipotent, god sees everything.

He watches everyone when they masturbate.
He watches everyone when they pee.
He watches every rape, every murder, and every crime and does nothing.
He watches every show on TV and listens to every radio station 24/7.
He watches every preacher who uses his name to fleece those who love him. And he's OK with that.
He reads every newspaper, every book, every email, every blog, every site, and every post, including this one.

And he does this on every inhabited planet in the universe.

Actually there are various explanations for the infinite being, none of them are universal.

There's the Clock Maker God
There is the Puppet Master God
There is the Caretaker God...

Theologians have argued for literally millennia about which ones are the "true" god.

the situation.

Dad used to hate the passage about "knock and the door shall be opened...". He called it the "Santa Clause God" concept. I suspect it was in part because he was more of the "clock maker God" kinda guy. Some people are fairly consistent in their point of view.

the problems of omniscience in a universe clearly more vast than the “globe and sphere” religious cosmology. See for example Lucretius.

About 1,500 years later it got all problematic all over again.

In every dimension. Putting aside the physical scale you mentioned, the first couple of generations of stars from our patch of stardust are a little outside the bounds of a humanocentric deity. And there's every indication the universe will continue long after Earth gets consumed by our sun. That's a lot of time at both ends which is utterly wasted if the inhabitants of one planet on a middle-aged third generation star are the sole purpose of the universe. There are some unflattering words for believing that all of that matter for all of that time was purely for the entertainment of some over-developed primates.

All of creation is a part of the Creator. And be extension, all of us share a part of the Creator by being a part of the creation. That we cannot understand it is a reflection of our human limitations rather than any proof of the Creator's limitations.