This situation is only not nightmarish because the woman is attractive and the man is a pushover. Unfortunately it would be completely unacceptable to have a story where he was attracted to someone else and was upset that some random albeit talented demon woman insisted their marriage was fate.
The author treats it as normal, but there's an undercurrent of like abuse to the whole thing.
The girl was locked up for years just because she has horns?
The girl using her future sight power to get the MC to agree to things?
etc etc
I think the only "nice" explanation for the motivations for the second one is that she's destined to die after the future she's seen has come to pass and she's speeding things up to spend more time with the MC.