fused relatives versus interrogatives

Would you differentiate which are relatives and which are interrogatives? (And I want to know the sub-category (sub-name) of each below, if they are.)

1. “You can keep it,” said Harry, laughing at how pleased Ron was. (Harry Potter and the Sorcerer's Stone)
2. Disgusted that the Slytherins had lost, he had tried to get everyone laughing at how a wide-mouthed tree frog would be replacing Harry as Seeker next. (Harry Potter and the Sorcerer's Stone)
3. His questions showed me how complex and mysterious were certain institutions of the Church which I had always regarded as the simplest acts. (James Joyce, Dubliners)
4. "I don't give a damn how you lost it as long as you keep it hidden." (Ralph Ellison, Invisible Man)
5. We revenged ourselves on Leo Dillon by saying what a funk he was and guessing how many he would get at three o'clock from Mr. Ryan. (James Joyce, Dubliners)
6. The duties of the priest towards the Eucharist and towards the secrecy of the con-fessional seemed so grave to me that I wondered how anybody had ever found in himself the courage to undertake them. (James Joyce, Dubliners)
7. I noticed how clumsily her skirt was hooked at the back and [8.] how the heels of her cloth boots were trodden down all to one side. (James Joyce, Dubliners)

As Dr. McCawley says:

It is often difficult to distinguish free relatives from interrogative complements, and indeed many examples are ambiguous between the two interpretations. (James D. McCawley, 1988. p.431)

It’s very difficult to distinguish which is relative and which is interrogative. A Korean blogger says, how in “How I spend my free time is a private matter.” is a nominal relative [free relative or fused relative], but in “I want to say how pleased I am to receive this award.” it's an interrogative.

This differentiation is somewhat easy: for the first how functions as CGEL says “combines the function of head of the NP and precuclear element in a modifying relative clause.” And the latter how functions as not referring to something known, something concrete, which can be specified (source).

Solution 1:

A very good question.

Basically, the more chunks you cut away from a clause,
the less likely you are to be able to tell it from
a different kind of clause that's been sliced up just as much.

There are two kinds of embedded Wh-clauses.
Haj Ross calls them Conjunctive and Disjunctive Wh-clauses.
The difference is essentially the difference between

• a relative clause, which is presupposed (therefore conjunctive),

and

• a question, which is indeterminate (therefore disjunctive)

• Conjunctive Wh-clauses (A and B and C and D and ...)

  1a. Who Sandor photographed ...
  1b. Where he developed the film ...
  1c. How much he was paid for the negatives ... is fantastic to the kids.
  1d. What they shot at him with ...
  1e. Why he wants to write it all up ...

• Disjunctive Wh-clauses (A or B or C or D or ...)

  2a. Who Sandor photographed ...
  2b. Where he developed the film ...
  2c. How much he was paid for the negatives ... is a mystery to the kids.
  2d. What they shot at him with ...
  2e. Why he wants to write it all up ...

The distinction seems to be triggered by the predicate governing the Wh-clause.
If it's factive, like be fantastic, it's conjunctive; otherwise, like a mystery, it's disjunctive.