Starting in the Studios then moving to the main Park seems like a good plan to me, we often do that. It sounds like you're familiar with the California Disneyland (and maybe Florida?), so if you want recomendations of stuff you won't have tried before, be sure to go for Ratatouille, Cinemagique, the new show in Animagique, and (if you like coasters and have time) Crush's Coaster. In the main park, you'll be familiar with most stuff, but our version of Buzz Lightyear is noticably better than the American ones, and spend some time exploring the upstairs section of the Castle and the Dragon underneath it. Hopefully you'll still be there in time to watch Dreams, as its a really great show

Do some attractions have limited hours?
The storybook boat ride and Casey Junior close earlier than everything else, I think.
Does DLP have any coin-operated orchestrions, mutoscopes, fortune tellers, or other such old-timey mechanical arcade things?
Unfortunately not really. There are games arcades but they only have comparitively modern games - DDR, Daytona 2 etc. The closest to what you're asking about would be the "flatten and indent a penny" style machines and the "Monnaie de Paris" gold coin vending machines, which are modern but in a vintage style design and build. As a side note, I collect the coins, and the are really nice - and only 2 euros each

The machines are scattered around teh park - theres some in Disney Village, some in the main entrance area of the park under the hotel, and some in the arcade walkthroughs.
That said, be sure to check out the Art of Animation building in Studios Park - that has some genuine old machines with animation clips played from flipping card/photos - like the old "strip-o-gram" penny viewers, as well as other interesting old machines, including one of only 2 remaining original Disney multiplane cameras in the World.
Any must-try snacks?
You can get a deal in the parks from various places dotted around where you get a hot drink and a brownie (or similar) which comes in a re-usable plastic thermos style cup for around 6 euros - quite good value and you get a souvenier out of it

Not really a snack, more a full meal, but if you get time I'd thoroughly recomend the Annettes Maxi Incredible Burger from Annettes in Disney Village - a huge 600 g burger with fries, best I've ever had, and if you manage to finish it, you get a free milkshake!
Also, check if there is any concert on at Billy Bob's (again in the village) on the day you are there, the live entertainment there is free and often excellent, and the fixed price meal is only 13 Euros for a main, desert and drink.
I don't know how long your day will be, but both Annettes and Billy Bobs are open after Dreams and the parks close
