Side trip to Mallorca from Barcelona? Skip side trip to Tangier?

The first three sentences of your post make for a great itinerary. Resist the need to add more destinations and enjoy your journey.

When I planned my first trip to Spain (Andalusia), I thought about Tangier. My research ended when it appeared that it was akin to being in Los Angeles and taking a day trip to Tijuana. . . kinda far and not representative of the country, just a touristy border town.

Even without Mallorca, your trip is very fast-paced. 3 nights in Barcelona equals 2 days, one of which could well be affected by lack of sleep and jetlag. Then you've got a string of one and two-night stands. Going to/from Granada is especially time-consuming. If you're driving, it might work. By train, I just don't think you'll have enough time to see even the major the sights.

Thanks to you both. It is helpful to read your comments.

Slow it down a bit.
"My 12-day trip to Spain includes 3 nights Barcelona, with Dali/Figueres side trip."
Add an extra night in Barcelona and make an overnight on the Costa Brava - Cadaques via Girona, and return via Figueres.
"Fly to Mallorca for 2 nights because my parents went there 50 years ago."
Drop it - this is your trip, not your parents.
"Fly to Sevilla to explore Andalusia for 6 nights - Cordoba (1), Granada (2), Ronda (1), Arcos, Sevilla (2)."
This is perfect.

Tangier is culturally quite different from Spain and not so much considered the "Tijuana of Morocco" as it used to be. As much as I would like everyone to visit Morocco, I would save it for a different trip. Architecturally, the Moorish palaces at Granada and Sevilla are more impressive than anything you will see in Tangier. (If you decide you have time for Morocco there are now good budget flights options such as Barcelona-Fes that might work at least one way.) You don't need Nerja, Tarifa, or Gibraltar and Mallorca also would not make (has not made) my list.