That sort of training isn't really the norm. it is pretty hit and miss at an mma IMO.
All the time. JKDers love it. I have never seen any one get hurt.
I don't know what a PE fist is, But I don't think that the idea is to have some thing "more serious" as much as it is to make extra sure that people are hitting correctly and using palm strikes when necessary.
Sure but the ring is only one environment with a different set of rules than the street so you have to explore other environments with a different mindset.