"Couldn't there exist different laws of gravity for big things like planets and small things like rocks, which explains why I've never seen rocks attracted to each other?"

Yes, there could in some alternative universe, but not in this one that we know of, and it's not necessary to explain why you don't notice rocks being attracted to each other.

There could exist some difference between "microevolution" and "macroevolution," but not in this universe that we know of, and it's not necessary to explain species.

The entire concept was made up by creationists to try to add a patina of science to their deeply-unscientific beliefs. And the problem with an unscientific world view is that science will never change your mind about things, you'll just decide what science to accept and which to not accept.