About the last non-repeated sentence in 爱人是行船人
Cross-posted on Quora this morning, and the answer came in soon. I was told "ui" means "prick" (the verb, not the noun), so I turned that into Mandarin 刺, and my reference gave me 揻, with precisely that sentence as an example: 心肝像針揻。Sim-kuann tshiūnn tsiam ui. (心像被針刺一樣。); (other example: 揻一空　ui tst khang(戳一個洞)). So that's it.

Literal translation: My heart feels like pierced by a needle.
Singable translation: A needle's piercing my heart.