Ok deep questions here I don't have a solid answer for the first question but the others are there.
I am not sure, there might be official docterin on that but I haven't found it, I have wondered myself about it. My favorite theory at the moment is along the lines of Time Travel/cyclation
God(our God) made the Universe we are in, but he made it from more "Primal materials" as I understand it.
So, think of it as each God being a Father to their perspective Human population, just because they are a Father doesn't mean they are Our Father, We have One Father and One God, the others while there, are not ours.