Erjdriver.
Unfortunately I do not have the knowledge to answer your first two questions and hopefully the active pilots and students will be able to provide you some useful guidance.
However, concerning your 3 week holiday wouldn't it be better to re-order the visits? I would suggest flying into Barcelona, hiring a car there (try EasyRentACar quotes) and then driving to Madrid, then into Andalucia, then into Morocco and then back up to Barcelona, for example following the Mediterrean coast (Malaga, Marbella, Alicante, Valencia, Tarragona...) because I belive one can't drop off an EasyRentACar at a different location than the pick-up one. However, perhaps with another company you could drop off the car somewhere else and fly back from there. Alternatively you could buy an InterRail type system ticket for x number of days that RENFE sell at any main station (I could get you more information about this option). The train system works fairly well, and you can of course knock down on expenses this way travelling by night.
Hope this helps.
jl