Hey jeddere, to answer your questions:

With power chords, as you said, its personal preference, I play with finger one and then three and four, although I used to barre with my third finger, so just play it the way it feels most comfortable. Also, it will get easier to move chords quickly with practice,

When picking, it is okay to rest the little finger on the scratch board for support, i rest my little finger and ring finger for extra support. You can rest the wrist on strings that are not being played, i don't think its a bad habit.

Also, as for bad habits, try not to hold your pick slanted when strumming the strings, make sure it points straight down, thats a bad habit I used to have.

hope that helps