All of the Dwarf rings are accounted for, either through destruction or recapture. This is mentioned many times in Lord of the Rings, for example Gandalf's words in Shadow of the Past:
Seven the Dwarf-kings possessed, but three he has recovered, and the others the dragons have consumed.
That the ring of Thrór was the last one that the Dwarves possessed is also well recorded; in the Council of Elrond we see Glóin saying the following:
The Seven are lost to us – if Balin has not found the ring of Thrór which was the last...
And also Gandalf's story of his visit to Dol Guldur recounted in the Quest of Erebor (published in Unfinished Tales):
I had entered Dol Guldur in disguise, and had found there an unhappy Dwarf dying in the pits. I had no idea who he was. He had a map that had belonged to Durin's folk in Moria and a key that seemed to go with it, though he was too far gone to explain it. And he said that he had possessed a great Ring.
Nearly all his ravings were of that. The last of the Seven he said over and over again.
This establishes that the fate of the seven Dwarven rings was quite well-known to the Wise.
Sauron kept the three he had recovered for potential future use as bargaining tools; we see an example of this in the story of the messenger from Mordor that Glóin recounts in the Council of Elrond:
Then about a year ago a messenger came to Dáin, but not from Moria – from Mordor: a horseman in the night, who called Dáin to his gate. The Lord Sauron the Great, so he said, wished for our friendship. Rings he would give for it, such as he gave of old.
As for the destruction of the other four, I'm not aware of any source text that explicitly states which dragons had destroyed them, or when they were destroyed, although a hint is given in the Appendices (to Lord of the Rings) recounting the Dwarves stay in the Grey Mountains:
But there were dragons in the wastes beyond; and after many years they became strong again and multiplied, and they made war on the Dwarves, and plundered their works.
How this can be reconciled with the statement in the Silmarillion that "it is said that the foundation of each of the Seven Hoards of the Dwarf-kings of old was a golden ring", I do not know, although the use of "it is said" here is telling: this is evidently a Dwarven origin-myth and perhaps should not be taken literally.
This is essentially all the information that Tolkien ever gave about the seven. We don't know who the other two Dwarves that Sauron recovered the other two rings from were. We don't have clear details on when the other four were destroyed. We don't know which Dwarven households originally held them.