IIRC, there's a custom power called Aura of Power or something, that automatically applies a an aspect to every scene you're in. It's a [-0] power, with the caveat that you don't get any tags. That would be one way to handle the Myrk. Upgrading it to [-1] for a free tag per scene would probably be a reasonable upgrade.
Everything else looks good. Keep in mind, they likely have the Catch of Light, which may complicate gameplay with other PCs who aren't averse to light. Maybe make it so that their Toughness/Recovery simply doesn't work in bright light, but as changelings they aren't harmed by it.