My most recent visit to Andalucía was too long ago to be helpful on logistical matters, but I don't think I've ever seen a comment to the effect that Arcos is preferable to Ronda. Ronda has a very dramatic setting along a gorge.
I'm with you on liking to stay in one place and take day-trips, but you'll be spending a lot of time going back and forth to train or bus stations in Madrid and Seville, so do keep that in mind when choosing your lodgings.
For rail schedules and fares, check the Renfe website, I see that there's an excellent option to Salamanca that's much better than your 2-1/2 hour trip. The 8:55 AM departure takes only 96 minutes! The Salamanca trains have quite varied running times, so that's a destination for which you'll want to plan a bit ahead. That said, I would rank Salamanca behind Toledo and Segovia in terms of interest for the average traveler, though it has a large historic district. (I haven't been to El Escorial.)
Fares on fast trains (including that 96-minute run to Salamanca) do increase as you get closer to the departure date, but on shortish trips, you may reasonably judge that the flexibility is worth the 10-20 euros or so extra you may pay if you wait to buy your ticket in Madrid or Seville. You should check fares for this Saturday or Sunday and compare them to prices in early June to see how much the fare varies. The slower trains (whose fares do not change) will not yet be listed as travel options in June.
The train to Toledo is an AVANT and has a fixed price. The train and bus stations in Toledo are a considerable distance from the historic center (though there are escalators to take care of most of the climb), so you should assume it may take you an extra 30 minutes actually to get to the historic center if you don't take a taxi or find a well-timed bus up the hill. Rick warns that the last train and/or bus back to Madrid can sell out, so you might want to buy your return ticket at the same time as the outbound. Toledo is fascinating; I recommend staying as late as you can. The bus to and from Toledo takes about twice as long as the train, but it is a viable option if for some reason you can't get a train ticket. The station for the Toledo buses is at Plaza Elliptica, which is likely to require a Metro ride from your hotel, however.
For Segovia, note that the AVANT and ALVIA trains take almost exactly the same amount of time, but the AVANTs are about half the price of the ALVIAs.
If there are no trains, check for bus options. Rome2Rio can be very inaccurate about trip duration and fare, but if you keep drilling down it will usually provide a link to the appropriate bus company's website. If not, try Googling "Bus Seville to Ronda", etc. Even more than trains, bus service tends to be cut back sharply on Sundays and holidays, so examine schedules very carefully to be sure that you don't end up with a tricky bus trip to be made on a Sunday.
I believe Samar (Los Amarillos) is a major player in Andalucía. You can check its bus schedules here. In Seville, the bus station you want is Sevilla-Prado S.S., not Cruce Sevilla. It appears that the summer schedule hasn't been loaded yet, but I see March buses to Ronda (1-3/4 to 2-3/4 hr.) and to Arcos (2 hr.).
If you are absolutely sure that you will be switching from Seville to Madrid on June 6 (that's my calculated date, based on your original post), you might want to go ahead and buy that ticket. There are two trains that day with 20-30 euro tickets available. By comparison, AVE tickets for tomorrow are 76 euros. Don't buy unless you're certain of your travel date, because the promo tickets are non-refundable and non-changeable.
