A few devotion questions

So um yeah I am going around with your run-of-the-mill aether/fire AAR/Dev sorceress and I’ve got a few questions mainly about the devotions I take:
1.Is Scales useful on caster or more like does the skill from it works with spells?
2.Since I am not taking Rhowan’s Crown it it worth to up demo mastery enough for Agonizing Flames?
3.Is this devo choice viable in anyway?
4.And if not is the Aeon Hourglass really the only path to aim to?
5.Is Devastation worth putting more than 1 skill point?

Thanks in advance to anyone kind enough to answer