like most people, this kind of thing is an interest for me not an area of expertise, so I hope I have an open mind ;-) I would like some further information though. You say that "Modern students in the field now ponder at least three separate waves of Immigration to the Americas, roughly between 10,000 and 30,000 years ago." I may be out of date, but I thought that there was no undisputed evidence of any pre Clovis (circa 13000 BC) inhabitants. If you could point me at any good summary of evidence to the contrary I'd be very interested.
"Some Native American legends look back to the earliest arrivals as having been some 30,000 years ago." Yes well, legends are probably less use than folk songs as a record of history!
As you say, there is a dearth of evidence and the greatest danger it seems to me is that of academics making a reputation for themselves by pushing a particular viewpoint based on a narrow specialisation.