The spells all seem to working as intended now. Including fixing the problem of multiple Active Effects that I had for a while (needed a flag set not to show the initiating spell in the UI).
My progress is getting slowed because Kothet is enjoying his time in Tamriel, especially as his housecarl is a hottie! He's just trying to complete his set of Legendary Daedric Armour, because he's clearly trying to impress someone, and all he needs is one more Ebony Ingot to temper his cuirass. However, he mined out Gloombound making Ebony bows to grind up his Smithing, and he's had all the ebony from Northwind Mine (found two dragons at the summit afterward - the resident one had company). We found at least half the veins in Blackreach, and his game doesn't include Solstheim, so not many sources left.
The housecarl is mute right now (maybe that's why he likes her!

) I need to put together a voice for her, with lines from another housecarl, maybe. Aranxa's male housecarl uses the regular CrDremora voice that the summoned Dremora Lord uses. He's vocal, even when she's trying to sneak.

We're not sure if he resents being in the complete control of a female, as he's too dutiful to suggest it. Aranxa loves it, and his lines just crack her up.