Way. Too. Early. He's an idiot and gets toyed by the situations. I'm not saying he should stay single. If he changed his mindset and wants to commit to a relationship, he should do that, by all means. But now he willingly got engaged. And he asked her himself. He has no idea, if things will work out between them. They might and surely there have been a handful of close calls that got them closer, but those are feelings forged in extreme situations. These things are special and would deepen an existing relationship and strengthen its bonds. And if things will work out, they will do exactly that. If they'll do. On the other hand there is an age difference, she is basically still a fickle child, mischievous (He still didn't realize how much (date rape), but he already has an idea.), and there is the cultural difference. They are literally born from different worlds. They also don't know each other that long and does he know anything important about her background? No? Maybe that's because he doesn't know her for that long.
Date her. Be in an relationship with her. Move into the same home (or tavern rooms). It's all fine, but don't propose to her. ...Yet.