I'd like to see an additional night (total of 3) at Siracusa. I think Noto's probably easier to visit from Siracusa (or on the way to it, I guess, if you can protect your luggage in the car while it's parked) whereas Modica and Scicli are easier to visit from Ragusa. Siracusa has a rather large medieval district (Ortygia--which is where you want to stay if parking isn't too much of a challenge) as well as an archaeological museum and archaeological park. Of all the places I went in Sicily, Ortygia felt like the nicest place just to be. It's a super-atmospheric place just to wander around in the evening. However, if you can manage to stop off in Noto (which is quite small) on the way to Siracusa, you can manage with just two nights. Keep in mind, though that if you aren't big on Greek ruins and don't plan to trek to Agrigento/Segesta/Selinunte, the archaeological park in Siracusa (with a Greek theatre) is an easy way to see something along those lines without having to go far.
The major area you haven't mentioned is the interior. I think it's sort of a shame to spend as much time in Sicily as you have and see only the coast. Piazza Armerina looked like an attractive place as I went through it on the way to the Villa Romana del Casale (great Roman mosaics), Enna was very quiet at mid day--like a step back in time, and Caltagirone is known for ceramics. I'd happily trade off some of the planned Cefalu time to see a bit of the interior, but I don't care for beaches and acknowledge that you may have very hot weather in June and a beach break would be nice.
Three nights in Taormina is longer than you need for seeing the fairly small town, so that's another place where you might steal a night. I would much, much prefer to have more time in Siracuse than in Taormina than the reverse, but plenty of people love Taormina (thus the mobs of visitors), and I assume it's a lot nicer at night.