Thanks, yeah, I have been having a break ...
1) Unfortunately, ~を…にも知られないのは運が強い does not help me. I don't have a problem with the ~なくて part, or its connection with what follows, but with the reason for the passive form with を. I know I have had problems before with this kind of pattern.
It seems to me that「屋敷妖精たちにどんなにひどい仕打ちをしているのか」is what is known (or in fact not known) by『日刊予言者新聞』の誰. So why is it を not が?
3) No. However, for context/flow reasons I wondered if the potential interpretation was completely apt.