Immortality is impossible. You'll die of something else if it isn't old age. Even your copies will die, and the means for making them will be destroyed at some point or succumb to entropy.
I think he meant "Why don't we solve dying of old age first". I think that is pretty obvious from context.
Entropy is non-decreasing in closed systems. Also you can make a habit of not keeping all of your copies in one solar system.
Would you really think of all of these "copies" as yourself?
Right. Immortality is impossible without indestructibility. The mean time from birth to a fatal accident is probably around 200 years. But indestructibility is worse than mortality - imagine yourself stuck forever in a situation you can't get out of, like being accidentally buried inside a slab of concrete. What a boring life that would be!
Christ you just described the nightmare scenario I've been having since hearing the possibility of the universe being infinite, which would mean a consciousness exactly like mine is stuck under a pile of stone somewhere.