Well, I for one am quite certain we can exclude the third option.
Let's think this through.
Should Melkor indeed have mystic powers that can identify these monsters, it would be a great loss to dispose of him right away. However, it makes little sense for him to reveal his powers right away. If he truly is a seer, which I'm inclined to believe, as it is a story to crazy to make up, surely he won't live through the night. I wonder, why not use that eloquence to convince us not to kill him without revealing his powers?
At the same time, if his devious mind has come up with this masterplan, and he himself is in fact part of this pack of wretched creatures, we are in for some dark times. Surely his own wolfish friends won't slaughter him during the night, and he can claim that they didn't do so to throw further suspicion on him. We'd still be clueless whether or not to believe him.
Right now, I believe that regardless of whether he is a seer or not, we shouldn't do the dirty work for those monsters. I'm sorry Melkor, but I fear your powers are too dangerous for those wolves, and they will kill you during the night, but during the day, you shouldn't be harmed by us. My vote stays on Rokapoke, and I urge everyone to do the same.
Don't let those monsters play us out against each other by having us kill our most potent weapon against them: knowledge!