A built-in command was added, also using "genie" (because it made sense and I didn't think it was worth avoiding the name conflict with this script). You can switch to "genie item pocket" to use the built-in command, or you can use "genie.ash pocket wish" to keep using the script.
Sadly, no, that would be easy. There's a spreadsheet on the forums somewhere where people are reporting failed and successful wishes (both for monsters and for effects), but that hinges on people trying and reporting their findings for some obscure monster/effect.
Genie.ash has built-in lists of monsters and effects that have been reported as unavailable, but that is only as accurate as far as people actually telling goes, and as such, just as speculative as the above spreadsheet. (Though, I have seen cases of people getting confused/frustrated because an effect/monster showed up in the list and wouldn't happen, leading them to think they were doing something wrong).
And on that note, Ezandora: none of the war heroes can be wished for.
Other critters that can't be wished for (someone please let me know if there's a better place for these):
any slime tube monster (slime tube monster, slime, slime colossus, etc.)
any gingerbread monster (gingerbread alligator, gingerbread gentrifier, etc.)
None of the fantasy realm +rubee effects or boss requirement effects can be wished for (I just verified):
* Fortunate, Son
* Faerie Fortune
* Heroic Fortune
* Fantasy Faerie Blessing
* Brewed Up
* Poison For Blood
* Fantastical Health
If someone makes a blacklisted effects spreadsheet, I'll happily enter this over there, but meanwhile--blacklisted effects:
* Industrially Frosted
* Slicked-back do (at least, as the relay script tries to wish for it, just wishing for "Slicked-back do" manually gets the other effect with that name)
* Behind the Green Curtain
* Avatar of She-Who-Was
* Avatar of the Storm Tortoise
* Avatar of the War Snapper
* Fortunate, Son
Genie is offering "Tainted Love Potion" for moxie, but this appears to be blacklisted. Also, for the benefit of anyone else who ends up here and wants to modify their own list: the blacklist is in KoLMafia\relay\choice.1267.ash