Sauron's trips to Sammath Naur

[Landroval]

Yers the evidence is circumstantial.

We have no single refference where the nazgul act against Sauron's will; we have at least two refference concerning the obedience relation between them. I guess we have different understandings of the word.

But I would like to see "much better" explanations to the facts given.

Please read post no 6.

Yet the quote says the Nazgul were absolutely subservient to Sauron, but he had only primary control of them.

Wrong, this is the weak point in your argument. It never says "only", it is strictly your adition, and taken in the context of the letter and not only, this addition is unwarranted.