Boy, you do seem to be having difficulty with getting this trip booked. All of the companies you mention are good and quite reputabe, but since time is the major issue, have you checked ShoreTrips? I know they offer Stingray City tours that fit your time frame. There is a 2 snorkel stop that meets at 10:45 and a 3 snorkel stop that meets at 9:15. I believe either of those would work. Here is a direct link to those specific trips:
Hope this helps. Keep us posted.