About the job prospects and skills learned during physics/math PHD
As a preamble, I don't quite understand why you suggest that fundamental physics is connected to high energy physics since the bulk of recent foundational experiments have been done with lasers and atoms, but to each his/her own.

The large majority of physicists work in industry and do quite well, as you can see from the salary chart below (source).  



Employment tends to be related to solid state technology, information technology or optical technology (the areas that produce the largest number of graduates) but even graduates in less industry-obvious specialities like high energy physics find industry jobs. 

The running joke is that a physics and an engineering graduates are sitting next to each other at a graduation ceremony.  The engineer is happy to get a degree, but the physicist replies that he (because there aren't that many female graduates) not only got a degree but also an education.  

PhDs in physics have a capacity to reason abstractly and comfortably deal with the abstract.  As a PhD candidate, you will have to learn a good deal of programming on various operating systems.  You will be faced with challenges of data integration (or data fusion) and data interpretation, understanding filtering of data etc (especially true if you do high-energy phenomenology); these are but examples of a number of techniques that have wide direct industrial applications, irrespective of the field you specialize in. 

Transitioning to industry is not necessarily hard, but you will not get an industry job because your thesis was on 10-dimensional supersymmetry: some flexibility is required.