I think it's irrelevant whether the argument is valid because the conclusion reports only what "seems" likely to your interlocutor, which is not particularly interesting.
There's no (known) objective probability measure over all metaphysically possible worlds. So the probabilities (chances) in the argument you report must be subjective, which is just to say that they express the idiosyncratic opinions of the person advancing the argument. If you happen to have different opinions, then there's no reason for you to accept the argument's premises.
Moreover, it's not even clear that subjective probabilities can be defined for all metaphysically possible worlds. Probabilities are defined on sets, and there are too many metaphysically possible worlds for the collection of all of them to form a set (they form a proper class). For example, for every cardinal number x, it is metaphysically possible that I have experiences for exactly x seconds after I die; and the set of cardinal numbers is too big to form a set.
(Incidentally, this answers your title question: the set of metaphysical hypotheses cannot be enumerated. The set of metaphysical hypotheses is too big to form a set, let alone a countable set.)
In sum, the best case scenario here is that your interlocutor has deduced some consequences of his/her idiosyncratic opinions, which you might not and need not share. The worst case scenario is that the premises of the argument don't even make sense (i.e. they're not reconcilable with standard ideas about probability, sets, metaphysics, etc.).