I'm not sure about the route you plan to take. Andalucia is likely to be very (unpleasantly) hot in early September, so I'd push that area--especially Seville--as close to the end of the trip as is practical.
I hate to see Toledo (especially) and Cordoba as day-trips, but you only have so much time, and I can see that you can't really afford to spend 3 nights in each of those places (though I thought they were worth it). I will note that in my view there's more to see in Toledo than in Valencia or Malaga. I'd be sorely tempted to eliminate one of those two. I enjoyed both of them on my most recent trip to Spain, but I had six weeks to divvy up between Andalucia and my second recent trip to Catalunya.
I doubt that Segovia and Avila are practical in a single day by public transportation. I imagine there are bus tours that combine them, but I don't recommend taking one of those. What pay extra money to be stuck with someone else's scheduled distribution of time between those two cities? I say Avila isn't worth visiting unless you're going to be driving past it in a car, in which case you can stop for an hour or so. Otherwise, it's just a wall. There's a perfectly good wall in Girona. You don't need to make a trip to Avila, and cut Segovia short, in order to walk on top of Avila's wall.
There's more to see in Bilbao than in San Sebastian, though the latter does have that magnificent beach. I would definitely not try to cram Bilbao and Getaria into one day trip. Is that some weird bus tour? Don't do that. There are frequent public buses between Bilbao and SS. Just use those. Zarautz/Getaria/Zumaia are pleasant places. If you had time, you could see all of them in one day by bus and train. But they don't hold a candle to Bilbao. The latter has a much larger historic center than SS, and with very few tourists.
Girona is in no way a 1/2-day trip. Or at least it shouldn't be. It's worth an overnight or two--but at least a full day: walkable wall, large historic center, art museum, two historic churches, Jewish history museum, and (apparently) a bunch of really good restaurants.
There is no Salvador Dali Museum in Barcelona. The Dali Theatre-Museum is in Figueres, farther north than Girona. There's fast rail service as well as cheaper service on slower trains. The DTM will not be a quick visit for you, as an art lover, and I recommend seeing the (included) jewelry collection as well. There's no way I'd want to combine the DTM and Girona on a single day-trip, though I know some people do that. It's a mistake if you're really interested in art (there's the art museum in Girona, too). Girona makes a nice base for visiting Figueres.
There are a couple of museums in Sitges as well. I think one of them may have very limited opening days. That doesn't seem like a 1/2-day trip either.
Skip the Ramblas beyond the time you will almost certainly need to spend on it to reach some of the places you want to go. It's just a wide shopping street popular with pickpockets. Spend your extra time in the Eixample, enjoying the sprinkling of modernista buildings.
Have you gotten hold of a guidebook covering your cities? Your list of sights reads like it came from descriptions of city tours. I think you're missing some things you'd really enjoy that probably don't get hit by tour groups. Just a few examples:
The Sant Pau modernista site and the excellent MNAC art museum in Barcelona. The latter has some wonderful medieval frescoes rescued from churches in the Pyrenees and an interesting modernisme collection featuring jewelry, furniture and decorative arts.
The Basilica of San Juan de Dios and the Rodriguez Acosta Foundation in Granada.
One or more of the Casa de Pilatos, the Palacio de la Condesa de Lebrija and the Palacio de las Duenas in Seville.
The Thyssen-Bornemisza Museum in Madrid. I haven't been there, but others have recommended the Sorolla Museum.
