Regarding Aunt Marge's inflation, I don't remember ever reading in the books that she was ever restored (deflated). Nor was it seen in the films.
Did that ever happen? Or is she still out there, floating?
Yes, Aunt Marge was successfully deflated!
"Eat, Harry, you look dead on your feet. Now then... You will be pleased to hear that we have dealt with the unfortunate blowing-up of Miss Marjorie Dursley. Two members of the Accidental Magic Reversal Department were dispatched to Privet Drive a few hours ago. Miss Dursley has been punctured and her memory has been modified. She has no recollection of the incident at all. So that's that, and no harm done." [Cornelius Fudge, Minister for Magic]
Prisoner of Azkaban - page 44 - US Hardcover
In the film, Fudge basically gives the same speech as quoted above when Harry arrives at The Leaky Cauldron, as if he's dictating a letter to Harry. In the film they do not show Aunt Marge being deflated. Fudge just notes that she has been and that her memory has been modified.