5) I think Riddle can’t use Parseltongue to prove stuff. You can always suspect that you’ve been False-Memory-Charmed to remember Riddle speak in Parseltongue. (Even Harry could be charmed this way, Riddle just needs to ask a minion to do that.) That means Riddle most likely has some other way to make credible threats, at least to Death Eaters, and Snape is a Death Eater.
6) To single out Lucius, Riddle could provide evidence that Lucius was not Imperiused to become a Death Eater. Since that’s the truth, and Riddle was the one who didn’t Imprerius him in the first place, such evidence shouldn’t be too hard to find.
Possible motive for burning Narcissa could be infidelity, or betraying the Death Eaters to Dumbledore, or any number of other reasons why people kill their spouses. Accusing Dumbledore is the obvious move after that, because no one else would be brave enough to kill Lucius’ wife in the middle of the war, and Dumbledore had a clear motive (see Ch. 82).
5) I think Riddle can’t use Parseltongue to prove stuff. You can always suspect that you’ve been False-Memory-Charmed to remember Riddle speak in Parseltongue. (Even Harry could be charmed this way, Riddle just needs to ask a minion to do that.) That means Riddle most likely has some other way to make credible threats, at least to Death Eaters, and Snape is a Death Eater.
6) To single out Lucius, Riddle could provide evidence that Lucius was not Imperiused to become a Death Eater. Since that’s the truth, and Riddle was the one who didn’t Imprerius him in the first place, such evidence shouldn’t be too hard to find.
Possible motive for burning Narcissa could be infidelity, or betraying the Death Eaters to Dumbledore, or any number of other reasons why people kill their spouses. Accusing Dumbledore is the obvious move after that, because no one else would be brave enough to kill Lucius’ wife in the middle of the war, and Dumbledore had a clear motive (see Ch. 82).