The probability that God exists depends entirely on your priors. After all we have no observable evidence to consider. I would give it a very low prior, because it's such a weirdly specific belief, considering all the possible origins of the universe.

The probability we are in a simulation depends on a bunch of assumptions. Assuming specifically we are asking about a "historical simulation", that the parent universe is identical to ours, we can change the question. Instead ask what is the probability we will someday create historical simulations of our past.

Technology certainly seems to advance over time, and the upper limits on computational power are extremely generous. So it's possible we could someday have the technology to do it. Assuming that, then it just depends on the probability you think we will want to make simulated beings. Something about that seems kind of sick and immoral, so I am skeptical of that assumption.

But if it is true, then the probability you are in a simulation is extremely high. Because the number of simulated beings could easily be orders of magnitude higher than the number of actual 2016 Earth inhabitants. Provided that many different simulations are run.

God in the religious sense probably does not exist. On the other hand the existance of type II creatures (that can manage and direct the energy of whole galactic clusters) would not surprise me the least. Their interference with human evolution and deeds would not be shocking too.

The quantum machanics behave disturbingly close to lazy evaluation - so this would not be surprising too.

Everyone of us is a god to a colony of ants.

Did god invent humans or was it the other way round?

Define God?