To repeat the down-pick you will need to return to the original position by moving your pick up, towards your head. This up-pick will not sound or connect with the string, though, so consider it a ...

As for the powerchords used, Bb5 isn't in the commonly used E Aeolian mode (E-F#-G-A-B-C) or even the spicier E Phrygian mode (E-F-G-A-B-C). The latter mode is more relevant here due to the F5 ...