Yeah, the Carrows were terrible pedagogues from what little we saw of them... I don't think they're qualified to teach at all! (Though I'd probably also argue Snape isn't exactly qualified to teach, either, given how much he seems to hate the students...)
The Boggart ward also was a thing in year 3, during the Christmas escapade at Godric's Hollow! Lord Charlus used it to deter wandering Muggle kids that his brother Henry had taken in during WW2.
I'm glad you figured it out that quick re. Astoria! That girl chooses violence every day...
The Maiden's Kiss being caused by drugging kids with bond enhancing love potions is a commentary on how some Purityworld fics sandblast off all the personality from a character to make them fit into the ship du jour for the fic. The journey to make Bellatrix Lestrange fall for Lily Evans organically would take too long and force Bellatrix to deconstruct blood supremacy (Mother Magic forbid!) so let's speedrun it with the power of authorial fiat love potions! It's totally romantic and very feminist!
We will hear from Myrtle, but not quite in the way you expect!
In Cece and Dottie's defence, the memory they dredged up of Tom leaving Cece was very upsetting :P
Hagrid's the one who got the Acromantulae to the table. I imagine it was like... a splurt of web :'D