King Naugladur, breaking down what you said, first regarding Nargothrond:
In 'The Children of Hurin", it is said that the Petty-Dwarves hated the Exiles, for the Noldor had stolen their lands. We also know that the Elves did not understand that the Petty-Dwarves were incarnates and hunted them down for sport. Furthermore, we know that, while the other Dwarves resented the wrongs done to their kin, they were eager to work with the Elves, because both sides had gains from the cooperation.
There's no information that Finrod behaved that way regarding Nargothrond. Even Mîm didn't accuse him of that kind of behaviour, let alone any other Dwarves.
Looking second, at the issue of Húrin and Túrin:
While Turin had no rights on Finrod's hoard, Hurin ought to respect Turin's promise of paying a ransom to the Dwarf and not slay him. Moreover, Mim's betrayal was done in order for the Petty-Dwarf race to live a little longer, since the Orcs had Mim's surviving son as a hostage. Finally, Mim betrayed the Outlaws, but demanded Turin not to be harmed.
I think there was some confusion earlier, about whether Túrin had any claim on Finrod's hoard. You appear to be saying that it is just an issue of Húrin sparing Mîm's life, on the grounds that his son had done so at an earlier time. But one could argue that the deal between Mîm and Túrin was broken because of the betrayal of the former.
While Mîm demanded that Túrin not be harmed, did he honestly think that Morgoth and Sauron were beings of their word? This is a place and time with no equivalent of the Geneva Conventions. While the Orcs promised that Túrin would not be killed, this allows a lot of latitude to Morgoth, who can do what he likes, as long as he doesn't kill him. Gwindor is a particular case in point. Húrin could have pointed out (if he had been in a mood to talk) that Mîm by his actions gave his son a possible fate worse than death. Of all people, Húrin
knew what it was like to be kept alive but tormented by Morgoth.
Looking third, about Thingol:
Coming to Thingol, what I suggested is that Thingol demands a compensation for the Kinslaying in every sort he wants and later, after the Sons of Feanor demanded the Silmaril, they enter negotiations concerning its surrender by Thingol to its rightful owners.
It doesn't seem that Thingol was interested in any compensation from the sons of Fëanor; all he wanted was to have as little to do with them as possible, including banning any use of Quenya. By contrast, he allowed into his kingdom his four grand-nephews and grand-niece, Galadriel, whom he felt had nothing to do with the Kinslaying. Also, he kept in touch with Fingolfin and his people, whom he felt had atoned for what they did.
As before, I agree that he should have given up the Silmaril to the sons of Fëanor, as it was theirs. However, it would have helped if an apology had been given by Celegorm and Curufin, particularly the former, for their kidnapping and planned forced marriage of Lúthien.
Indeed, I'm very surprised that Maedhros and Maglor didn't get in touch and dissociate themselves from what their brothers had done, which was particularly disgusting behaviour for Elves.