1) Mortgage Interest and Real Estate Taxes basically skip Form 2106, and go directly on Schedule A. So you can just enter the $2500 as a rental expense, and $7500 as an Itemized deduction on Schedule A.
2) I have no idea why it asks you that, but it doesn't really matter. Checking that box may just ask you some additional questions. Just make sure that the $7500 shows up on Schedule A, and you are fine.
3) I think the taxes should be prorated. Use 3/12ths for a rental expense, and the rest as an Itemized deduction on Schedule A (see Question 1).
