Just sent this to Teslacon:
"Given the delays in vendor confirmations/denials for Teslacon I have accepted an offer for vendor space from another convention. Therefore, Otter Necessities will not be available to vend at Teslacon."
I'm very proud of myself for not sharing my candid thoughts, or taking advantage of the fact that my FaceBook persona is pretty disconnected from me, because I don't want to burn bridges. Not that I think Teslacon has left any bridges for me to burn at this point.
Feeling a little iffy about the decision, despite the fact that I'm well and thoroughly tired of feeling jerked around, and had been pretty much hoping we wouldn't get in, because then I wouldn't have to decide. But enough is enough - I could hope that we'd be treated better at the convention, ie: with basic respect, but I'm not seeing any real evidence that it would happen.
Still plan on attending Teslacon, since it does look like it is cool, and sources say attendees enjoy it.