Before we can actually test #2 we'd have to consider the parameters of what we are asking. We need to ask ourselves, "Just what kind of relationship does this God have to its creation"? For one thing, If God is eternally existing, if God is our 'sum of all that is real' then it means that our universe cannot be completely distinct from his essence.
Consider the following model of creation:
A craftsmen working on a rocking chair.
In this model, the materials of creation are completely distinct from the essence of the creator. They have their own existence. They are in actuality only manipulated by the creator. The act of creation consists in the creator having a vision inside their own mind that is independent of the manipulated materials, and acting to conform the materials to that vision.
This model cannot be the relationship between God and the universe, because then neither God or the universe can accurately be called 'the sum of all reality' anymore. You would have two separate eternally existing and yet distinct 'entities.' We would have to invent a name for the world in which the two exist, and we are back to a regression problem.
In otherwords, it may very well be logically possible that our God exists eternally and that our universe exists eternally, and our God has taken a strong hand in this universe, but then we still aren't talking about the 'sum of all that is real.' Do this God and universe exist by virtue of being part of a larger universe that itself is 'the sum of all that is real'? If so, is that 'larger' universe created by a 'higher' God?
These are logical possibilities which I exclude because eventually everything regresses back to describing a 'sum of all that is real' and it is only THIS final regression that I am describing. And so, however one works it, we arrive a position where the created thing is not merely manipulated by the creator, but rather its entire existence depends on the creator. Not just its form, but also its matter, and its energy.
In this final regress, if we are looking to describe the relationship between God and the universe, and we want to find ways to test this situation, we have to recognize that our relationship to that God is from the POV of being completely WITHIN that God. Whatever model we employ to understand our relationship with God will have to be consistent with that reality.
Some other things follow from understanding this relationship. For one thing, direct empirical observation is excluded on principle. We are within a system that is 'within' God. It is not possible, therefore it is not rational to expect, to be able to employ senses that can only perceive the system to perceive the sustainer of that system.
Again, its not as though we are standing inside a building, and the creator of the building is standing nearby. We would be 'within' the creation of the creator, but all the entities involved- you, the creator, the creation, share the same 'level' of reality. The actual relation to a God that is the sum of all that is real would not allow us even the logical possibility of 'windows' to see out of, because we can only see things that share the same type of reality that we have.
What this means is that the initiative lies completetly on God as to revelation. He can come down, but we can not go up. He can come in, but we cannot go out. The high can descend to the low, but the low cannot ascend to the high.
So, while it may be possible to conclude or infer the existence of such a being based on our senses, there is little else other than some basic attributes (omnipotent and omniscient relative to us) that we could infer. Things about nature and character and wishes and will would have to be revealed to us.
This is not a cop out. This is simply a fact. Atheists that long for empirical verification of the existence of this being are not properly taking into account the nature of the relationship we must have with this being, if he exists. Its not reasonable, its not rational, its fundamentally absurd. Other types of evidences must be sought, whether the atheist likes it or not.
But that is somewhat tangental.