I don't know how much of the universe is still invisible to us, perhaps the greater part of it we will never see. What then is the purpose of making something because it looks nice if there is no one to see it?
God can see it. Besides, doesn't the fact that we have seen perhaps only a tiny fraction of what exists blow your mind a little? Whether or not there is a God, even.
Ants are not self-aware. They don't contemplate their existence and so these questions don't matter to them. They do matter to us.
Presumably our level of awareness is not on the same level as an omniscient God, yes? Hence the analogy. Indeed, this is preciesely the point of that Psalm of David, of Job, of the Torah, etc - God's thoughts are not our thoughts.
I'm not following your meaning. The size of the universe would support what?
God's grace in dealing with mankind. The universe being large, complex, and largely not for our enjoyment would accentuate that God's relationship with mankind has absolutely nothing to do with our own intrinsic merit, but simply because God decided that's what he would do.
Final causation a myth? Once again I don't follow.
Most scientists would reject that there are final causes in nature. That is, 'why' is irrelevant in terms of intention or final purpose. 'why' only makes sense at a functional level - why do humans exist, because a set of biological processes over billions of years arrived at us. That sort of thing.
So the question ' why is there such a big universe' is irrelevant to science, unless the answer is something along the lines of "at cosmic expansion, x energy existed, and thus resulted in y amounts of matter, which formed z number of galaxies'. But it can't, and does not want to, answer questions in terms of final causes, i.e. "So that we would be amazed at the complexity of life/theuniverse."