gotta disagree. its because he's prince he knows how well these things work. he says it himself "i know waiting is best". id say hes rightfully frantic but this is probably the only thing in the story thus far that he actually has thought quite straight forward about. in the novel its very different though, so this moment is like major "redemption" for him
yes. its been a couple years since i read the novel, but IF im remembering correctly, the whole train thing doesnt happen. his entire redemption is kinda just from his time in her town & his family(more specifically the grandma) talking to her and asking for forgiveness on his and their behalf. so it was, in my opinion and apparently others, incredibly unsatisfying bc we didnt feel/see any real change from him as much as he is right now. id say they probably added this so it would be a more emotional reunion between them instead of somewhat forced forgiveness

He’s literally the prince of the country he could’ve had his aid go mobilize the troops while he searched for Erna but no he’s not thinking straight