The real problem is, in an infinite, probabilistic universe, even the smallest chance that God exists is a certainty. Of course, there is no shortage of conflicting, self defeating pseudo-science airheads that will believe anything else rather than making an attempt at living a Christian life with a little less ego.
I do not think that this "probability" means what you think it means.
I will try to tell you. No, it is too much, I will sum up.
Suppose you have an infinite barrel of marbles, 10% of which are green. Then the probability of drawing a green marble is (wait for it) 10%. This isn't a particularly small probability. If there is a single green marble, somewhere in the barrel, the probability of drawing it is asymptotically zero, statistically neglible, less than the chance of winning the lottery, and winning the lottery in one try is far from certain. If the probability that God exists is 1 x 10^{-403} in an infinite, probabilistic Universe, then the probability that God exists is (gasp) 1 x 10^{-403}. This is most definitely not certainty. Certainty isn't the "smallest chance", it is probability 1. It is the largest (possible) chance.
Even 1 x 10^{-403} isn't in the same ballpark as "the smallest chance", by the way. It is enormous compared to the probability that all of the air molecules in the room I'm in will suddenly (by pure chance) happen to bounce in just the right way to form a big blob of liquid air in the middle of the room and leave me gasping in a vacuum as air molecules outside of the house by strange chance miss all of the myriad pathways into the room. Which in turn is unbelievably, awesomely hugely enormous compared to the probability that the infinite, probabilistic Universe is in fact determined and known at the subatomic level by a perfectly organized, uncreated, omniscient, omnipotent, omnipresent superbeing that created it all by pure magic from nothing.
Oh, wait -- that's a contradiction, isn't it! If the Universe is infinite and probabilistic, then it can't be infinite and deterministic and hence known by an omniscient, omnipotent being, because there is nothing less probabilistic than something that is completely determined by an all powerful, all-knowing being. So your premises directly contradict your conclusion, in addition to demonstrating nothing more than the simple fact that you have absolutely no clue about probability distributions on continuous spaces.
Ego aside, you might want to contemplate learning something about probability and reason itself before you argue in favor of something empirically, logically, and statistically indefensible. God (as a concept) is all three.
rgb