Factual error: At the end, when the Doctor shows her companions the asteroid named for Rosa Parks, it's depicted in a dense asteroid field which looks absolutely nothing like the (very sparse) asteroid belt does in real life.
Factual error: Kandoka labour laws require companies like Kerblam! to have a minimum of 10% organic staff. The villain claims that, as a result, only 10% of humans are employed, at all. These are two completely different quantities: if 10% of the cars in one parking lot are blue, this doesn't indicate that 10% of all cars are painted blue, but that's effectively what the episode thinks. The fact that no-one else, including the Doctor, calls him on this further magnifies the mathematical error.
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.