oops just realized something, when I posted ----0----- ----0----- ----7----- ----7----- ----5----- ----0----- I meant: ----X----- ----X----- ----7----- ----7----- ----5----- ----X----- I was high
I would just barre the 5th fret so that it doesn't sound messy should you hit a different string. As far as your first question, I play most power chords with two fingers, so I think it's ok. Alex