I think you don't necessarily have to prove god's non-existence because there is no evidence. No one believes in the Flying Spagetthi Monster or the Invisible Pink Unicorn, although their non-existence can't be proven either.

But I think there is a disproof for a god that is allmighty, all-knowing and perfect and influences in the universe:
If god is perfect, he won't change his opinion, because either the old or the new opinion must be wrong and thus unperfect. So we know that god, if he exists, will never change his opinion.
At the beginning of the universe, god could choose the initial state of the universe and the natural laws, which would lead all events that ever happen if god does NOT influence in the universe. So, at the beginning, god could already decide everything that ever will happen.
So if god influences in the universe, he must have changed his opinion. This contradicts to the assumption that he never change his opinion and thus that he is allmighty, all-knowing and perfect and influences in the universe.
So god either does not exist or does not influence in the universe. quod erat demonstrandum.

And even if god exists and haven't influenced in the universe since he created it, the Bible is not the word of god. Then deism would be true.