Kgshrauder, the answer to your problem with ticketmaster is simple. That is the only seats they have with the number of tickets you gave em.
Anyways, invite only to opening night is not a disney only thing. Lots of shows do that. However, usually if they don't fill up all the seats via the invites then usually two to three days before they would sell em regularly.
Yes, the opening night of Poppins was invite only. As was Camron's other show that was opening up in the fall. That show would be Les Miserables and that show had some extra tickets available for the otherwise invite only preformance.
I would suspect that disney would be inviting people to thee last preformance ever of BATB.
"If you try to shag my husband while I am still alive, I will shove the art of motorcycle maintenance up your rancid little Cu**. That's a good dear"
Tom Stoppard's Rock N Roll