I want to know if you can use the teleport twice on the same unit. For example: You couldnt teleport your astroltih bearer because your dice was 1-2 so... could you use it again? I guess not but i prefer to ensure
You could even teleport your mage up, cast an endless spell, and then teleport him away. There are many amusing tactics available with Great Remember.
1-2 : "The unit cannot move or charge this turn" technically you might say so but it doesn't make sense to me
You are correct. It does not count as movement. Technically you can teleport a Slann on Balewind without losing the Balewind. As the Balewind states it is consider part of the model. This might be errated to say that models on a Balewind cannot move of be removed and replaced on the table while on a Balewind Vortex.
I see no reason why you can't, and I've toyed with the idea myself, my one concern would be failing the "return" cast and having a unit very exposed
I don't think this is the case. The balewind and the wizard riding it are treated as a single model after you cast Balewind.
You definitely can do it. I have done it at tournaments. They might errata it away, but for now it is legal.
How is it legal? They are treated as a single model, so you can't teleport off it because you would teleport the Vortex along with you. "I've done it at tournaments" isn't an argument...
The Balewind Teleports with the model because they are treated as one model. It doesnt matter that the model loses its move characteristic because LoSaT does not make use of the move characteristic. You can use a Slyvaneth Wildwood to teleport Slyvaneth wizards who are ontop of Balewinds as well.
My mistake, I thought you meant that you could teleport the Slann off the vortex and replace him with another model. I'm not sure why I read it that way.