Thank you! This clears a lot up in my head, never having done itPeening shouldn't be a particularly violent process. Normally you'd heat the exposed part of the tang and tap it quite gently. It may take more than one heat. Assuming the handle wood has the grain running from the guard to the pommel, it can take a fair bit of abuse as well. It's much stronger along the grain than across it. It's one of those things you pick up, different handle materials all react differently, what will take some abuse if you need it to and what will just break unless everything is fitted perfectly.
In that video it looks like he just glues the pommel on, I don't see any threading or a bump on the end?