I don't believe the universe is expanding and I believe it is actually finite
Well you see, it is expanding. Sorry that you don't believe it, but your belief does not dictate how the universe works. Nobody knows if the
entire universe is infinite or finite however, so that remains possible for now...
So in general, the reason that the speed of light is the limit is because light is always moving the same speed in every reference frame, even if you're moving 99% the speed of light, light will appear to move at the speed of light relative to you. If you were to go faster than light, then that would violate it. Universe no like violations. That's basically all of relativity in a nutshell.
There are theoretical particles that can move faster than light, but we have no evidence of their existence, and given that they would cause all sorts of paradoxes they probably don't exist.
no one has a clue what space is made of, it's hypothesised that it's dark matter
no, omg. Space is space. Space =/= matter. Dark or otherwise.