I like the PFF stuff, but I'll point out that if Jackson isn't playing in passing situations where he knows it's a rush situation, it seems to me that his rushing rating will be lower.
Put another way, who's going to have a better pass rush rating?
Player A - plays mostly on rushing downs and has to read a pass play on the fly.
Player B - plays mostly on passing downs and rushes the passer unless he reads a run on the fly.
My hope is that playing Jackson on passing downs will give him more opportunities to pin his ears back and actually rush, thereby improving his pass rush effectiveness (and PFF scores).