Extremadura tentative plans -- feedback?

I haven’t been to that region in years, but you plan seems solid. I like your two bases and that you’d take day trips from them to other places. If you didn’t want to drive all the way to Jerte upon arrival, you could stop in El Barco de Ávila. That would be 30 minutes less driving.

With all the time you have for Jerte, the following are places on my to visit list in that area: Muralla Medieval de Béjar, Puente Románico Siglo XIV and Castillo de Valdecorneja in Barco de Ávila, Monasterio de San Jerónimo de Yuste in Cuacos de Yuste, Cascada Bonal near Piornal, and Granadilla (half abandoned town. Residents were forced out due to dam construction. One can walk around. There also a castle there but I don’t think it is open to the public. Les than two hours from Jerte is Mogarraz. On the buildings in town are paintings of the people who used to live in them. Since you’re into hiking, just outside that hamlet is the Camino del Agua. There seem to be plenty of outdoors areas near Jerte. In Plasencia there is an aqueduct. Plasencia is only 24 miles from Jerte. Cáceres is just over an hour from Jerte so I doubt you’ll need to stop for lunch anywhere.

I've visited Extremadura twice (most recently in 2014), and found it to be quite interesting in its own right; I don't think additional ventures into Andalucia, or elsewhere, are required unless you have lots of time for them (and among just eight nights, you don't). The nature of a "wow" factor is judgmental; for me, that factor lay in the various quaint, historic cities of Extremadura that still seemed relatively undiscovered by tourist masses. (Though on each Extremadura visit I took the added precaution of visiting in November.)
Still, you may be packing a lot into just eight nights. It seems your four nights in Caceres, will be spread among at least four other "day-trip" destinations, which means a lot of moving around. If you're interested in ancient Roman ruins, Merida will require at least one night, with two justifiable. I would also recommend changing "possibly Trujillo" to "definitely Trujillo," especially since it's fairly close to Caceres. (Itself a beautiful town, assuming nothing has changed since my 2006 visit -- and I don't know why anything should have.)
Incidentally, if either of you is interested in chess, note that Zafra was home to Ruy Lopez for several years.

Thanks everyone. Still working on this--perhaps I should remove a night from Jerte and add a stop in Merida? We really prefer to settle in one place versus road tripping, but sometimes distances prevent that.

Mérida is a very easy day trip from Cáceres, the highway is fast and parking is easy. The roman theater, the bridge, and the monuments scattered between the theater and the bridge make a good day out combined with the museum, but that's about it for me.

Please don't miss the Real Monasterio de Guadalupe, one of the top 3 most important in Spain and a powerful religious symbol for much of Latin America, also a UNESCO World Heritage Site.

An easy daytrip from Trujillo or Cáceres‎.

That is firmly on the "maybe" list, thank you Carlos