Let us dissect this wonderful example of written German language:
Yes, your guess is right this is an example of using subjunctive ("wüssten") in reported speech.
In this case "doch" is used as a modal particle to gently shift the meaning of the surrounding sentence. Here it may be intended to achieve some empathy or even agreement for the fact that the people we are talking about do not yet know ("wissen"). I can't think of an English counterpart to this, it may be something along the line of "however", or using "could" instead of "did".
This adverb is a often used for a temporal restriction of the following negation.
They do not yet know (but they might know in the future).
Another adverb often used to emphasis a negation.
They do not know at all.
Thats unsual indeed. It seems like an antagonims but it may be intended in this case where the author possibly wanted to express in few words that it were many of a smaller group of people, like saying many of the few.