: Being at work, I have not my Tolkieniana to permit me to answer knowledgably on your questions regarding the Gond or Thu/Tuvo. But it is entirely possible for Morgoth/Melkor to have "created" or, more likely, twisted the false-faires for his purposes in the same sense of many of his other creatures or servants. Morgoth never "created" any species per se; for example, orcs were his creatures, but distortions or blendings of existing races (most likely elves), while other servants, maiar such as Sauron or the Balrogs, were beings drawn to his service and distorted to foul ends. I suspect that false-faires were more likely the latter, although there appears to be no definitive answer in Tolkien's writings. I know of only a few brief references on the subject.

I think that false fairies as another name/use for 'evil Maiar' that went around and through the races spreading fear and dissonance is a good idea, although I hadn't heard the term before! But I just finished reading the Silmarillion and am just starting Lays of Beleriand so I feel a little more 'polished up' than usual on the subject! Also, regarding Thu, I believe that Christopher Tolkien (explictly, maybe, I don't have the book with me) clarified that Thu was definitely a pre-manifestation of Sauron in JRR's early works. That is, Thu is Sauron with a different name.
Hope this helps!
Patience