@"If you believe that there are things that science cannot prove, then you should also accept that God could exist."
Science can't prove any theory. It is in the busines of disproving theories. There will never be proof of the theory of gravity, for example, merely proof that all the alternative theories we can cone up with are wrong.
The precession of the orbit of Mercury disproves Newton's theory of Gravity, Einstien's theory (general relativity) correctly predicts the precession.
God is untestable, you can always say that god created any evidence you detect, so no matter what, you can't disprove god. Therefore the theory of god is unscientific. Technically, you are then correct that God could exist. Fortunately you CAN twst theories of any specific 'God'. You can test our Thor, Zeus, Yahweh, Allah, etc. Each may be disproven. Each text which is claimed to be 'the word of god' can be shown to be false.
Likewise, the idea that this Universe is merely a simulation is untestable, any evidence we coould come up with to prove this isn't a simulation, could be simulated. Thus it is unscientific. Likewise with 'God' you can still test specific 'simulation' theories, and if the evidence is there for them, that is good evidence for reality being a simulation - we don't have any solid evidence for this theory today.
But on a philosophical level, it doesn't matter if this is a simulation; we definitely exist, even if we exist as a similation, that is still existance. Even of this were a just some dream, we would exist as a dream. We must still act like reality is all the is.
And in any case this doesn't address the unquestion 'why there is not nothing'.