Yeah, some awkward writing at the start there. "You know what's coming for you. You've always known"... wut?
"Theon, I have your sister. If you don't submit to me here and now, I'll kill her"... wut?
And then Euron goes from superjerk to full retreat mode in the same scene. That didn't seem to fit his character... even if it did, why announce it? Why not just save face and then no call no show. Would seem more in line with his personality.