There's a discussion on creating custom moves that represent difficulty, first thing in the Advanced Fuckery chapter (p. 268-9). You've got the basic idea already, and your suggestions map right on to some of the ideas. To summarise the ways you can made a move reflect a difficult task:
You can make a general move that lets you change the difficulty with a -1 or -2 when "things are tough", but most groups find this custom move boring/annoying/not a valuable addition. (This one isn't relevant to you particular case but here for completeness.)
You can cover difficulty into a more specific, but still general "when the NPC is strong" move, treating it like the NPC is interfering with a 10+, giving the PC's roll a -2. This is a totally legit thing to do as the MC in Apocalypse World and matches one of your ideas. Just give them a -2, because reading Uncle Richard is just that hard.
You can make a move that just layers itself over another more basic move, modifying its outcome. Something like, "when you're trying to read Uncle Richard it's acting under fire, and the fire is: Uncle Richard is disappointed in you." This can have whatever variations you can think of, and is just like one of your ideas.
You can roll difficulty right into the substance of a move, saying "when you read Uncle Richard…" and then giving a new, more interesting, tailored, but ultimately fictionally disadvantages list of options on 7-9 and 10+.
You can mirror an existing move or make it a subset of options, as you suggested above, but to do it cleanly just crib the options and make it a move all to itself without mentioning the basic move. If you want to do it with style, change the options so they reflect the idea that this move doesn't get you want so easy, making the choices tougher, meaner, and more interesting in their focus on this particular person.
All that is to say, you've got the right idea: make a custom move, however you like, to reflect Uncle Richard being damn inscrutable. Either just make it work, or make it cool, but make it.
And of course, you can always just say, "Yeah, ok. But doing that is Acting Under Fire and the fire is Uncle Richard is disappointed in you." That's just fine for ad hoc difficult situations. When you're finding you want to do that every time a particular circumstance comes up, then that's exactly when you should be (as you were) thinking of making a custom move for it.