Is there any reason for me to not bite the bullet and take this as a reductio showing that God couldn't have created v?

Well, we need to distinguish 'creation' in two senses:

First creation (emanation, bringing about of being, creation ex nihilo): This refers to the initial giving of being (either temporally or in terms of its "procession"/"emanation"/"giving" from its ultimate source). Plato and classical platonism identify this activity with the form of the Good/the One.
Second creation (formation, crafting, shaping, designing the world): This refers to the arrangement of disorganized being already present into an intelligible, orderly, lawful world. Plato and platonism often identifies this activity with the demiurge and/or the henads. You can assign angels to this role (as Tolkien explicitly does is his cosmology). It is the usual idea people have of God's (or gods') creating the world and is most of the account of creation to be found in Genesis.

Provided that distinction is sufficiently clear the problem doesn't seem solved. Did the One have to emanate this demiurge or could he have emanated another?  In your language *this* creator and not another would have to be necessary and I'm not sure that saves real possible worlds- certainly not without introducing a notion of libertarian freedom somewhere.

Is there a real distinction between the being only one possible world and everything in the world being necessary? It does seem to me that if there's only one possibility then that's the necessary one. Or am I fudging a formal distinction with an informal one?

Suppose there is only one possible world. Besides its alleged counter-intuitiveness, what's wrong with it?

Tomislav Ostojich wrote:

Listen to the central claim of modal concordism: possible worlds actually exist. But then they're not merely possible worlds anymore.

I agree. That does seem a valid worry.

Let me see if there's a way out.  We could make a distinction with respect to the kind of being that they are. You would say that those are actual possible worlds, as opposed to constructs or fantasies or some other unreal way of construing possible worlds. This would be similar to saying that something like platonic forms are formal realities not things in the way that a rock is a rock but not imagined or otherwise unreal entities in the way that say a painting of a rock is.