Flying open-jaw Barcelona-Madrid (choose multi-destination option when searching flights).
Which tour - Best of in 14 days or My Way in 11? Either way, you'll spend time in Madrid so you probably don't need more days there. Just take an afternoon or evening train and spend your last night there so you can get to the airport easily. If you stay at the Europa (one of the RS tour hotels), there's convenient public transportation just meters away.
There is so much so see in and around Sevilla, you could easily fill another week. Jerez and Cadiz are easy day trips from Sevilla by train, and there's a lot to see in Sevilla that the 14-day tour doesn't cover. Cordoba is my favorite Spanish city and a good place to stay for 1-2 nights and take it a little slower after the tour. Please don't skip the Mezquita and Juderia there, as an overnight stay, a day trip from Sevilla, or a stop on the way from Sevilla to Madrid (there's luggage storage at the bus station across the street from the train station in Cordoba).