Physics and bio departments tend to be the most toxic. Students have no BATNA.
Come to think of it, the news stories I remember (just off the top of my head) of advisors pushing their students to the point of suicide were chem. advisors.
(2) Quant hiring is super-competitive. most physics students wouldn't get jobs. A lot of quants are physicists, but the converse isn't true.
(3) And students? Not so much. Quants like to hire Ph.Ds or possibly ABDs.
Ones who are ALSO good programmers can go the CS route, but most aren't. You need to do basic programming to do physics, but not industry-grade software engineering.
Most don't want to do the work (not implying laziness -- it's about interest / fit / etc.).