Alhambra tickets sell out months in advance for peak periods. November is definitely not a peak period, but two weeks is still not early enough to buy tickets. You should nail down your Alhambra ticket immediately if you know what date(s) you have available. General tickets are already sold out for November 16, 17, 23 and 30.
Other places I'm aware of where advance purchase of tickets may be necessary, either to avoid long ticket lines (they can be 1+ hours) or sell-outs:
Barcelona (in addition to La Sagrada Familia): Parc Guell (no tickets sold at park), Casa Mila/La Pedrera, Casa Batllo, Picasso Museum, and Palau de la Musica Catalana (English tours sell out). I don't know whether the current security situation in Barcelona will cause a lot of people to change their plans, making advance purchase of tickets less necessary.
Seville: Alcazar and Cathedral. Alternatively, for the Cathedral you can go to Iglesia del Salvador and buy a combo ticket.
Madrid: Some folks suggest pre-purchasing tickets for the Prado and the Palacio Real. I don't think they sell out, but sometimes there may be a wait to buy tickets.
You should not expect rail fares to come down; as far as I can see, all tickets have been loaded for the month of November. Prices are at their current level because others have already bought the cheap tickets or just because that's what they charge for AVE tickets.
Buses are a viable alternative for some shorter travel legs, but if a direct AVE is an option, it will be a great deal faster. For example, between Barcelona and Madrid the AVEs take between 2 hr. 30 min. and 3 hr. 10 min. The regional express takes over 9 hours. Looking at fares for the morning of November 29, I see that you could save about 35 euros by taking the regional express train, but it would cost you 6-1/2 hours. That doesn't seem prudent to me.
The round-trips to Toledo and Segovia will cost the same no matter when you buy your ticket. The only concern there is the possibility of sell-outs. Rick particularly mentions that possibility on trains returning to Madrid from Toledo. You can monitor the situation on Renfe.com to be sure trains are not being flagged as sold out.
All your other trips are subject to increasing rail fares as you get closer to you travel date, unless the fares have already reached the maximum.
Buses can sell out, but it is not terribly common. As a solo traveler, you are in a somewhat less risky situation since you only need one seat. I've seen bus fares in Spain that looked as if they were not fixed, so I think there's some price risk if you wait till the last minute to buy bus tickets. Also note that it is standard policy to stop selling bus tickets X minutes before the scheduled departure time, so don't cut it too close. I think "X" is 5, but I could be mistaken.
I can give no guarantees but would expect it to be safe to buy bus tickets a week in advance as long as you don't mind possibly paying a bit more for them.