i got my visa with double entry for a 6 month period of validity, with each entry max 90 days. they had no questions, i just had to indicate on the form that i wanted a double entry. it just cost a little more.
i booked my flight at a very low price just one week before my flight, although i was flexible on the date. it's worth checking out how much you would pay if you bought tickets for the next weeks or month - maybe price won't be higher than if you booked it far in advance.