Baby is healed with first personalized gene-editing treatment

From an evolutionary perspective it‘s interesting how the further medicine gets, the more we inherit genes unfit for life without medical support.

No, it would not depend on the sex of the baby, as the chromosomes that you're editing aren't X or Y.

Evolutionarily, the inheritance of genes is a far slower process than the medical advancements we make, so what I think we're seeing here is a chasing down of the low probability events. In that, most of the evolutionary pressure is coming from things like dirty water and bad food, but as we're solving those low hanging fruit, we have to go to lower probability events to make progress that feels equally important.

Also, if I am wrong here on the answers to the questions, please correct me!

Organs in your body usually keep some very old cells (formed in the embryo) around which act as parents for all the new cells in an organ. Any cell can only divide a limited number of times, so they typically maintain a "tree structure" where the old cells create children and grandchildren (etc) that then differentiate into the organ-specific cells that do the actual organ work.

If you modify only the differentiated cells, eventually they die, and are replaced by descendents of stem cells; if those stem cells didn't get modified, their descendents will not have the fix, and the treatment efficacy reduces over time.