This is a nice vid but there are two things to note.
1. he does not mention Callisto in place of Europa. Europa gets enough radiation to kill you in a day where on Callisto you would not even get the radiation you get here on Earth.
2. It might be possible to puff up a given asteroid by creating a cylinder within as he points out, but filling it with water and then heating it from outside and once it’s molten the water will expand and blow the asteroid to a larger size. It may be possible to turn a 1 mile wide asteroid into a ten mile wide habitat. I do not know how well it scales up to larger asteroids.