It feels to me like every story of the Dresden Files has a positive note in there. This tends to render most metal songs a bit unfitting; they tend to the dark side.
Likewise, any actually positive song is out (as a story themesong) because the stories do tend to have the negative side too.

That said, there's no reason to ignore them for personal themesongs!

For Molly after Cold Days, I am partial to Oonagh's "Märchen enden gut" (fairytales end well). The German distracts a bit as Molly is certainly not German, but the sound and essence seems to fit to someone who is holding on very hard (and possibly failing in the future) to the idea that even through the bleakness, fairytales will end on a positive note.
Alternatively, Frozen's "Let it go". Not nearly dark enough for Maeve, but Molly "unchained" would fit with the song.

For Mother Summer/Winter, I'd go for Celtic Woman's "The Voice", with a upbeat sound but also such gems like "I am the voice of your hunger and pain".

For Mab, Within Temptation's "Ice Queen". Should be obvious enough. Though it could be applied to Mother Winter as well.

For Lasciel, Within Temptations "Angels". Again, pretty obvious - it is all about a false saviour of a fallen angel. But it has the deception angle too - this is not an obvious dark angel like many of the Denarians' partners, it's a seemingly helpful angel who turns out dark (and who gets a proper kicking at the end of the song).

For Butters, Prince of Egypt's "When you believe". The realization circa Skin Game's end that, indeed "who knows what miracles you can achieve, you will when you believe". Plus a bit of Hebrew thrown in for good measure.

For Uriel, Prince of Egypt's "through heaven's eyes". Nothing says Uriel quite like this song's sense of: in the big picture you're doing great, but sorry, you can never understand quite how.

Probably with the myth and stories about romantic love. There is a lot of believe invested here and that is power.

And not in motherly love?

I suspect if you make a fair summation it's below romantic love in mythical intensity, but we're looking for a difference in not just degree.

What are the angels and gods supposed to be? I remember something early in the series about all non-terrestrial creatures being denizens of the never never, so I’ve always viewed all of these magical beings as variants of faerie type beings.

Eh, they're distinctly not a faerie-like being.

I think it's Bob, but otherwise Lash, who explains Angels are all-Soul. I don't remember the specifics of where I read the rest, but apparently Sidhe (and presumably other Faeries) are Body and Spirit. Humans have Soul, Body, and Spirit.

What this makes the Queens given their Soul-having origin is anyone's guess.

Avernite,

I can see Maggie Sr as being a conduit from the Vampires to the Wouncil.  I'd bet that the Vamps knew who her father was and they were looking for a better representative from the Wouncil than a dark sheep like Maggie Sr.

I could totally see them not telling her that they wanted to take over Humanity.  That may have been why she finally broke free from Lord Raith.

That is more or less in line with what I think, except I don't think Arianna and Lord Raith would involve their pawns in the beginning of their planning.

Then again, it wouldn't surprise me if this plot was long-lasting enough that the 'dinner' was nowhere near the beginning and yet it was still the same plot played out in Harry's war with the RCV.

Yeah, I've noted that connection previously. Longinus's name doesn't show up anywhere else; the Gospel of John simply states "One of the soldiers..."

Nowhere in the bible; Christian martyrology (both east and west) does refer to him.

That is what I think is happening now.  I think the vampires were trying to be the ones to take over from Winter.  The dinner that Maggie Sr, Ariana, and Lord Raith were at was the beginning of the planning.

When Eb wouldn't attend, the vampires decided that the Wizards had to be taken out so as to allow the Vamps to be able to create more troops for the defense of the Outer Gates.  Thus the plans for the War with the Wouncil.  But it was started a bit too early and they weren't able to put them away quickly enough.  The spell at Chichen Iza wasn't just to take out Harry and Eb, but all Wizards.

The question is, what was Maggie Sr's plan there?

As in, I can see why the RCV and WCV would want to take over from Winter, but not what they'd do for Maggie. She wasn't called LeFay because of some long-term hatred of all things Faerie, so that isn't a reason - in fact, it seems a counter-indication of her being part of some plot to displace the Faerie Courts.

A far more logical story, to me, is that the RCV and WCV were plotting to displace the White Council from its pre-eminence (as a prelude to taking over the Outer Gates and the human world), and Maggie wanted it displaced too (as a prelude to her installing a new organisation on human Wizards). This worked together nicely until their secondary motives started to clash - Maggie did not want a bunch of vampires to rule the human world any more than she wanted that from the ossified White Council.

Truth B
Molly and Harry?  "Oh but she's not a child now so why won't Harry bang her?"  Okay, okay, listen to me: Molly is still a little girl.  Small children never grow up - aren't any of you guys and gals here parents?  The little ones stay little forever, if you were a parent/guardian/close adult relative type of person to them when they were little.  Harry was an uncle-type to Molly for long enough that when he looks at her he sees the child.  And he'll always see the child - at least for like the next hundred years, by which time Charity will have been dead for long enough that he won't have to worry about her coming back and haunting him.

I would argue this kind of association is mostly subconcious. And Harry's subconcious has no problems at all with seeing Molly as a grown woman (as evidenced by Skin Game). So I am not sure how 'Truth' this is.