Melancholy makes sense there, if the music is supposed to show that Ladybug is sorry about the butterfly being used for evil. It still points in mostly upward directions, and there's the swell right at the "gotcha!" point, so it's being presented as heroic more than sad, at least in my opinion. But there's plenty of room for dad as the primary motif here.

I hear what you're getting at with "Not Alone". (At least, I'm guessing you mean the bits that play underneath the choruses? If not, I might need a specific link to hear the right riff.

I think the theme scoring will depend on who ends up with the properly functional Miraculous. If it stays where I think it's going to, and that a previous user turns out to be so I think it is, I would expect a theme that is going to evoke, primarily, the idea of undying loyalty. Not necessarily with romantic love attached, either. I'm not sure how that would work, but I wouldn't be surprised if that one went for four on the floor as the beat pattern.

Even though they're not related as species, I wouldn't be surprised if whichever one of Carapace's themes that doesn't become the "official" one gets recycled to use for Sass. Either of them would fit.