You're welcome.
Going through some of your points. It is strange indeed that the author does not even mention the origin of the technique. You mention that Neuwirth makes it seem that the beads are made from mostly feldspar. Do you mean Neuwirth, or the author of this article, Otto Parkert? Because it is Parkert that stated this, and is quoted by Neuwirth.

I know very little about glassmaking, but I am learning constantly. However, am I right in thinking that when a bead is completely translucent, like some I found in Briare, that the material is mostly (or completely) made from feldspar?

Looking at the translated quotes in the book (which I forgot to look at), it seems I found a new clue to what is intended with the words Steinmassen and Strassenmassen:
Neuwirth translates this section as follows: "agate or stone and strass substances. The former consists as a rule of fine washed feldspar which has been freed of as much iron as possible by treating with acids, and a small amount of phosphoric lime. The strass pastes on the other hand consist only of feldspar"
Street, Strasse, strass.....

I was told that the Bapterosses actually needed so much milk for their bead and buttonmaking, that they started a dairy farm next to the factory.

About using the term pressing or molding. I see the difference, and agree with you. However, in most literature and in the places the beads are made, pressed beads is used a lot more to describe both regular molded glass beads and Prosser molded beads. It is a language thing...I do not think the German (or Dutch) language has a term that means 'molded' in the way it is used in English.

Thanks for linking to Howard Newcomb's beautiful beads. I had seen them before, but will enjoy them again.
If you have any recommendations on what sources would be good for getting more information on the technical process of the Prosser beads, I would appreciate it.