1. No spoilers about Gwen's recovery, sorry! As for the others, certain allies will be able to teach you skills or even briefly jump into fights to help you out. You'll probably start seeing that in 0.20.1 :)
2. No, the Boss Girls have to stay in their own home areas to keep them safe while you're wandering around! Also, I don't want to have to double the number of renders and animations I have to make for each of them ;P