I'm struggling a bit with the first one (God). You properly observed the conditional nature of the second (Nukes), but entirely overlooked the same in the first (God).
The Second: Destroy the World OR Get Rid of Nukes
The First: Belief in God is Irrational OR Conceive of an Experiment.
In addition to this oversight, the premise is not quite right. It should read: "No conceivable scientific experiment could decide the issue of whether there is OR IS NOT a God "