Hmm isn't it against code of ethics for a doctor to treat their own family members? I mean, except for emergencies of course, so I guess in the back story for the doctor it has had to be an emergency I guess.
"It's not like I'm never gonna die" I mean, never of old age or illnesses with the things he speculates it'll maintain. So just violence to worry about mostly, though I guess suicide would always be an option.
here's a big secret - iron sand is basically shit quality and tamahagane is poor quality steel. Sorry to shatter your dreams but 1000 times folded steel is garbage because it needed folding