In a sense, pluralistic moral reductionism can be considered a robust form of moral 'realism', in the same way that pluralistic sound reductionism is a robust form of sound realism. "Yes, there really is sound, and we can locate it in reality — either as vibrations or as mental auditory experiences

In a sense it can't be considered robust realism. The two meanings of "sound" don't lead to any confusion in practice: we know that powerful hi fis produce a lot of sound1 and we know that deaf people standing in front of the won't hear any sound2.

However, morality is tied to the actions of oneself and others. There's no coherent situation in which gay marriage can be both right and wrong, because there is no coherent way it can be both allowed and forbidden. In practice we tend to just average out preferences when it comes to defining law and allocating resources...but the preferences in question might as well be subjective. It is difficult to see what is being bought by the objectivity in pluralistic objective reductionism.

But in another sense, pluralistic moral reductionism is 'anti-realist'. It suggests that there is no One True Theory of Morality. (We use moral terms in a variety of ways, and some of those ways refer to different sets of natural facts.)

Of course normative pluralism doesn't follow from descriptive pluralism. Some uses of moral terms be wrong. You said Craigs theological morality was wrong. If reducing and naturalising morality doesn't allow you to say anybody is right or wrong, what is the point?

And as a reductionist approach to morality, it might also leave no room for moral theories which say there are universally binding moral rules for which the universe (e.g. via a God) will hold us accountable.

Or, eg,, not via God. Unless there are: if you can say 1 theory is wrong, you can say N-1 are wrong and arrive at one not-wrong theory by elimination. So I don't see how your approach supports pluralism as a fixed principle: it can only depend on how things pan out in practice.