Ah a surprise for your mom and Paige sounds amazingly magical! I love the idea.
Omg I'm so glad you get to go to the audition!!
Hmm I think the one thing DBF and I consistently comment on about the performers in the parades is their smiles and their energy. Honestly, having not taken dance since I was like 12/13, I probably wouldn't notice if one of their steps was a little bit off or something. But I would notice if they weren't smiling or energetic because 99.9% of them are and it makes it so much better.
As for the 16 step movement thing, I'm not sure how useful my advice is on that front

I would just think that the more confident, poised and energetic you look, the better. Again, extremely limited dance background here so sorry, that's the extent of my suggestions!
When in June are the auditions? I'm sure you'll do fantastic! Not going in the parks will be hard I'm sure, but you'll still have a great trip! And meeting up with a friend from WDW is even better!
I 10000000% say go with photopass plus. I love love love the pictures we got from it in January. The photographers definitely take more pictures when they see the red card and they also offered us magic shots more. A lot of photographers told us, "Make sure you ask for magic shots whenever you stop for a picture!". We did 2 character meals where we got the package and they put the picture on your CD but also give you the printed copies. I didn't think it would make a difference to me having the print package since I had them on the CD and could print them on my own, but it's actually really nice to have the printed ones to take home. And the 1900 Park Fare ones came in a really fancy and cute folder (that also has the recipe for strawberry soup on it!).
The ride photos are fun too. There's always some funny ones that I want to buy but end up thinking it isn't worth it so I love having all of them, even the bad ones are fun to remember