I literally just finished reading Spinning Silver too, and as I put it down I said aloud "Wow I could have used at least one more scene with Mirnatius and Irina" because yes, exactly, I don't see the throughline from Irina rescuing him from the demon to them being in love or even having a really functional marriage.

I did end up being really there for Miryem/the Staryk king, though! The story did show its work there, I can see how it's going to work out, and I liked that rather than the original forced marriage he actually asked and she accepted properly.