I think you're way short on time in Palermo. The first day doesn't count (jetlag and sleep-deprivation if you're arriving from the US/Canada), so you only have two days there, and you plan to make two day-trips. While in Trapani you'll want to see Erice, so that will make for a long day-trip. I think the bus takes 2 hours from Palermo to Trapani. I'd prefer to spend a couple of nights in Trapani and see the area at a more relaxed pace.
I thought Cefalu didn't need a great deal of time (some others like it more), but Palermo is certainly more than a half-day sort of place. So I'd put most of your extra time in Palermo/Trapani.
Catania and Taormina are pretty close together. I'd try not to set up separate bases for those two. In any case, I think your time allotment for Catania is rather generous. (I feel the same way about Taormina, but I know it has big fans.) I'd transfer one night from Catania elsewhere--maybe to Siracusa.
I hate to see you have to pay for a private driver between Agrigento and Siracusa, but it looks as if it will be a lot faster than dealing with public transportation. You might check on the extra time and money to include a diversion to the Villa Romana del Casale outside Piazza Armerina. Maybe eat lunch in that town, too.
Edited to add:
A Sicilian I met at Monreale recommended the coastal town of Acireale to me. It's between Catania and Taormina. I didn't have time to go there but have since checked some photos on line. It looks very attractive. That's not the same as having stayed there, obviously.