[Kuruharan]

Being created in secret and in direct contravention of Erus rules by Aulë may also offer some insight into their moral center.

It had never occurred to me until now that this may be the reason for a dwarf’s secretive nature.

On the strength of that I think Sauron actually had quite a unique insight into the hearts of Dwarves.

It is an interesting idea. However, there is a question about it regarding how much he explained to his maia regarding the dwarves. It might not have been much more than he told the elves of Valinor, which is the source material for what we have.

the Dwarves were not completely dominated by their Rings of Power, it would seem that they were all lead to misfortune and evil ends by them

This is undeniably true. However, the Rings were designed to lead everybody to an evil end. In the case of Men, the Rings performed admirably and as Sauron intended. In the case of the Dwarves, they did not work as Sauron intended. In the case of the Elves they didn’t really work at all. I think from this evidence, one might conclude that Sauron had more of an insight into Men than anybody else.

Was there perhaps, one wonders a connection between Sauron's connection to Aulë and the siding of some of the Dwarves with him during the Last Alliance? We know that the Dwarves adhered strongly to "family". Is it plausible that Sauron played up his connection with Aulë (a sort of High Priest, perhaps?) to draw some of the Dwarves into his service?

It is possible, but I don’t think that any dwarf could have been genuinely ignorant about the reality of the situation. The Dwarves would have been harder to fool than Men in many respects, if for no other reason that they did maintain contact with their kin in the West. The Western Dwarves probably knew from the Elves that a former servant of their Maker was the chief lieutenant of Morgoth. While we don’t know, it seems reasonable to surmise that this information would have been relayed eastwards, especially given the amount of time that passed. When Sauron made his return to evil in the Second Age he made some effort to conceal his identity (at least with the Elves). Had he told the Eastern Dwarves that he had some connection to Aüle, that probably would have set off alarm bells (or something) with them. On the other hand, it may not have bothered them very much. But if it didn’t bother them, there is no reason to suppose that Sauron would have gone to any trouble to conceal who he was, especially if the Eastern Dwarves had adopted Morgothian aspects into their culture.

There might have been some sort of polite diplomatic fiction along those lines, but I think that by the time of the Last Alliance, nobody that had the sort of historical lore to draw upon that the Dwarves possessed could have been in much doubt about how things stood.

That somehow makes me think that it was not unusual for a rich dwarf to get spoiled and greedy.

That is probably quite likely.

One other thing about the Rings…it seems likely that the Eastern Dwarves would have received their Rings from Sauron himself as the Eastern Houses probably had little contact with Elves (particularly not the Elves of Eregion).