Let's say my threat level is at 42 and I am questing unsuccessfully for -10.

So my threat will go to 50 and Favor of the Valar triggers, setting my threat at 45.

Will I then go to 47 for the last two points from my unsuccessful quest or will I stay at 45?

Everyone I know plays that as having 45 threat left, though I can't think of anything definitive as to why.

Core rules say "Each player must raise his threat dial by the amount by which the threat was higher than the combined willpwer of all committed characters" . That's 10 in this case, so the threat dial would be raised from 42 to 52. This would ordinarily eliminate you, but then Favor of Valar's response kicks in and sets to elimination level -5, or 45.

1 hour ago, dalestephenson said:

Core rules say "Each player must raise his threat dial by the amount by which the threat was higher than the combined willpwer of all committed characters" . That's 10 in this case, so the threat dial would be raised from 42 to 52. This would ordinarily eliminate you, but then Favor of Valar's response kicks in and sets to elimination level -5, or 45.

Just to add, threat is raised in a chunk, not 1 at a time. Otherwise, ally Elfhelm would be absurd.

Thanks to all comments.