so, let's build this up one story at a time...
- darwinian poolroom: i think asimov is presenting the contradiction of god creating us to destroy ourselves as a sardonic joke directed at creationists, but asimov was a classicist, and he would have realized that the gods of the greeks and romans (not to mention the jews...) were indeed sadistic enough to take pleasure in that kind of wanton destruction. only christians of the augistinian variety, who insisted god reveals himself through natural law, would have seen a contradiction in that. in the various western indo-european pantheons, it is only the interference of other gods that save us from the trouble making gods (whereas the hebrew/persian conception of darkness is as interfering in our lives, and leaves us with the individual responsibility to reject it), who are intent on destroying us as an act of recreational amusement. so, beyond the sardonic joke, the discussion is ultimately arbitrary, both in how it defines god (there's no reason to assign god any specific characteristics, or to assume god is rational, or to assume god is just or ...) and how it discusses evolution in such an empty, unfalsifiable manner. i can't really offer a critique of the idea of god setting things in motion, other than that it's utterly untestable speculation, through and through, and that it doesn't conform well to the randomness that is inherent in how we understand the world (there is a concept of probability assigned to how those billiard balls behave, in truth). for these reasons, i don't think that the existence or non-existence of god can be deduced implicitly in this manner, and you're not really getting anywhere in analyzing hypotheticals, or arranging them in a hierarchy of arbitrarily perceived likeliness. rather, i think you just need to start with a null hypothesis and determine if you can generate enough positive evidence to reject atheism, or not. but, asimov isn't doing any of this, really - all he's actually doing is building up a punchline, which is something he does frequently in his mid to later period, with varying but usually unsatisfactory results. so, i mean, enjoy the dialogue if you want, but i don't see much of anything substantive in it. and, i actually don't think the idea of a god creating us to destroy ourselves is any sort of contradiction at all, even if i think it's utterly unnecessary hubris.