Sorry for the title, just trying to get your attention.

Ok I've got 20 gallons of apple cider going in my basement. I'm thinking of making some Applejack with a 5 gallon batch. I think that I want to oak it too. So here are some of my questions
1.How much final product should I expect from a 5 gallon batch (1 gallon...more?)
2. Should I oak it before or after I make it into applejack?
3. It finished at 7.3 ABV. What ABV would I expect in the final product
4. Is there any way to scientifically determine the ABV/Proof after I've converted it over to applejack?
5. Would there be any benefit (taste) to run it thru a Britta Pitcher charchoal filter?
Thanks