And I am befuddled by the idea that he would deliberately aggravate someone whom he's hoping can be prevented from killing him.
He was annoying, yes, but he's always annoying to mammals. Him deliberately goading Belkar into killing him doesn't fit with his last words.
Of course he knew what would happen. But he hoped that he could prevent it. "Maybe this time I'm wrong." That's how hope works.
If he didn't have hope, he wouldn't have wasted time with these explanations. He'd have said: "Of course your prophecy hasn't come true yet, you numbskull! Now kill me, if you think you've got the balls!" And he'd certainly haven't said last words that boil down to "Dang, I failed."
And that's why you try to "soothe" the murderer: because maybe he won't kill you.