4ZeN,

Q1 - It is as what takuya999 said, there is no need to transfer. The amount will automatically be deducted from your linked debit card if your Paypal balance is insufficient.
Q2 - I can't confirm this, I didn't calculate.
Q3 - You will be charged 2.5% currency conversion fee by Paypal on top of the exchange rate. For more information, check Paypal's Currency Conversion and Fees pages.