Good decision to fly from Barcelona to Granada.
When is your trip? Alhambra tickets sell out months in advance. If you can't get Alhambra tickets, on a short trip like this I would skip Granada.
Also be aware that Andalucía is miserably hot in the middle of the summer.
Assuming this is your first trip to Barcelona, I would definitely skip Malaga and apply that time to Barcelona. Your arrival day is likely to be pretty useless because of jetlag and sleep-deprivation. You certainly shouldn't pre-purchase timed entry tickets for that day. Barcelona has at least six highly popular sights for which advance-purchase of timed tickets is necessary to avoid spending an hour or more in line (and possibly still not getting a ticket). You may not feel the need to go inside all six of those problem sights, but most people coming to this forum seem to plan on a lot of them. Figuring out workable timing for multiple sights a day is challenging and tends to make for inefficient sightseeing because of snippets of unused time between the ticketed sights. Therefore, Barcelona is a city that's very difficult to blitz. I recommend a minimum of four full days there, which means you need 5 nights.
I believe the Damas buses between Seville and Ronda take 1-3/4 to 2-/34 hours. That would be a long day-trip even if you got a fast bus in each direction, but it would be doable. I don't know whether it would necessarily save a lot of time to travel Granada-Ronda-Seville, but it might. You can explore that on Rome2Rio.com, but don't trust the travel times, frequencies or fares shown on that web site. Keep drilling down until you get to the name of the bus (or train) company providing the service. There will usually be a web link. If not, use Google.
What I like about the day-trip option if you decide to go to Ronda is that it is something you can decide on after you've gotten to Seville and have an idea how much time you want for that city. It is very large and has a lot of sights that may interest you. Three nights there is just two full days and some hours.
I like Ronda, but you have to consider how much more sightseeing you can accomplish on your second full day in Seville if you travel to Seville the most expeditious way and stay there, vs. either detouring to Ronda or side-tripping to Ronda. The fewer cities you travel to, the more time you have to actually see things.
It's not a matter of whether Ronda (or Malaga) is interesting. Of course they are. But you have only ten real, usable days to work with. Paris and Rome are (more) interesting, and you don't have time for them, either. Such is the life of the traveler.