Spoilers---
btw i love this game so much
I'm gonna take a wild guess and say the husband drowned himself after they had argued and a the kelpies refencing what the grandfather memory when you venture into the lighthouse took the form of the MC husband that's why there's no scar on his arm because he doesn't know entirely what he looked like just the basics and the call that the mc got about something bad that happened was the help coming as referenced after they couldn't find the boat, they may have found the MC's dead husband and the non husband may have overheard that's why he might be trying to get rid of the MC referencing the knife being held to the MC's throat