With some of these examples - and this appears to be one of them - I have trouble seeing any difference between the two analyses. The difference is certainly subtle. Like you, I'd say this is an interrogative content clause.
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jooneyI think it can be a fused relative, but only by an act of the will.It's a joke. It says that it requires "an act of the will", i.e., an intense forcing of the mind, to make your brain understand that sentence structure (what he wants) as a fused relative in that context. The mind resists that way of understanding it and must be forced!
jooneyThank you very much for your help.You're welcome.
jooney"I know who you're looking for."Yes.
So here 'who you're looking for' can be interpreted as a fused relative, right?
You are looking for person A and I know that person.