Hi StudentRebel79.
You have an interesting itinerary. I don't think anyone can answer your questions except for you. Different people travel for different reasons. Some to take in the art and cultural events, some to take in the gastronomic events, others to take in the "way the locals live" while others try for a bit of everything.
I am in the process of planning a relative's trip here with his family. He has made it clear that they are not interested in the museum and arts circuit. They will be coming to absorb Spanish life the way that I absorb it. He doesn't "do" the art museums in the States, so why should he "do" them in Spain. So, you should ask yourself the following questions which I pose in response to yours:
1) (do you think these plans would be enjoyable?)
What kind of traveler are you? Do you know what you enjoy doing when you travel?
2) (Should I spend more/less time at any one place?)
Do you know what you want to see in each place? I tend to disagree when people say that you should spend xxx number of days in "Y" city and xxx number of days in "Z" city. It all depends on your specific objectives. If you want to visit all of the art museums in Madrid, for example, you will need more than four days. If you want to see just the tourist highlights of Seville, that could be done in a day.
3) (Is this too much traveling on off days?)
How will you use your travel time? If you use this travel time wisely ... to send postcards, write in journal, rest, plan your next destination, etc. No. Especially if you plan your long bus journeys on overnight busses.
4) (Any recommendations for festivals).
What kind of festivals are you looking for? Spain is varied in its festivals, from religious celebrations, bull festivals, neighborhood block parties (verbenas), food festivals, etc. Check out
Fiestas Atope . There are lots of dates there that should help you orient your trip.
Have a great one!