I realize you posted this awhile ago but here are my responses!
1.) No idea - I assumed it was some kind of kitchen utensil or just some wacky contraption invented for the movie. The boy using it was portrayed as being the "inventor/sciencey" one, so he may have invented it?
2.) Mope - the turkey/chicken neck turned me off!
3.) Loose vowels are when people drop vowels in their pronunciation of words. Think of the Southern American accent (y'all) or the Cockney accent ("libry" instead of saying "library"), and them compare them to the Queen's English accent.
4.) Sheep dye is real! Marie Antoinette used to dye her lambs differnt colors (usually pink or blue) when she "played" as a shepherdess. Think of the people who dye their poodles' hair different colors - it's just a hop, skip and a jump to dyeing sheep.
5.) I didn't see the special features so I'm not sure, but in the women's beauty world there are products called plumpers that plump up your skin to make it look fuller and less wrinkly (basically, they promote water retention), so it could be that. She also wore lots of prosthetics and pads as part of her costume, so she could be referring to that, as well!
#2.} {Whoops! "Mope"} I would LOVE to try this. My mom or my grandmother ALWAYS got the turkey neck & were always saying how good it was. I never got to try it!
#3.} OH! Like Eliza Doolittle vs. Henry Higgins in "My Fair Lady"! Or Lina Lamont vs. Phoebe Dinsmore in "Singin' in the Rain"! Now I get it! Thank you!
#4.} That's new to me. Thanks for the info - OH! Like the pink sheep in "Charlie & the Chocolate Factory" with Johnny Depp
I bet "loose vowels" may have been an off-color joke referring to loose bowels.
However, in seriousness, it also means badly pronounced vowels so you sound low class British.
As far as dying sheep, check out the movie "Blow Dry" with Alan Rickman. One of the character is practicing her hair dying technique by actually dying the wool on the sheep. It also helped the owner of the sheep identify his own animals.