Ever since I realized that physics seems to tell us straight out that we live in a Big World, I've become much less focused on creating lots of people, and much more focused on ensuring the welfare of people who are already alive.

I don't like that reasoning. If you create an interesting person here, in our hubble volume, their interestingness can reflect back to you. The other "copies" 10^(10^50) or so light years away will never have anything to do with you.