I called TWA again (and after 45 minutes on hold)I was fortunate enough to speak with someone who was both sympathetic and knowledgable. I was told that TWA had not yet released any FF coach seats (although several first class FF seats were available). She put me on a waiting list and said that it might be several months before the first batch of seats are released. She also informed me (which is the first I had heard of it) that I needed to call back within 30-45 days to "renew" my waiting list status or else I would be removed from the list. I guess that's a good way to keep those truely interested on the list, but you would have thought that someone would have told me this when I first was placed on the list!
Finally, I am happy to report that when I called United, not only was the representative friendly and knowledgable, but he had seats to ALL of their Europe stops available through May 8th, which was the latest their system goes out to. This experience has said a lot about both TWA and United! Thanks again.