You were quite close, but it's not 한폄 (no such word) but 한 뼘, that is, "a handspan". He actually says 한 뻠은 더 커서 그래. 은 here adds a little emphasis but also makes the sentence flow better. 뼘 means the width of the hand when fully stretched out, from the tip of the thumb to the tip of the little finger. It often means a small distance or gap rather than the actual length, as used in this example. Children like to use this word a lot in their play, like 한 뼘, 두 뼘, 세 뼘, etc. By the way, it's 김복주, not 김북주. "북" is almost never used in people's names :-)

thank you~ ^^

This is the link if anyone needs to visit: https://www.youtube.com/watch?v=7K_4g8GuvqY 니가 왜 불안한 지 알아-----> 니가 왜 불행한지 알아? What I think I have heard: 바라는 게 현실보다 늘 한편만 더 커서 그래