I have simmed multiple season, and the highest completion percentage I've seen is 57%. Most of the league is in the 40's. I have tried to increase Accuracy Globally by 10 but they made only a small difference. Has anyone else seen this?

That sounds like you've altered the passing stat modifiers, or you imported some QB's with some really horrid ratings or WR with really bad hands/height/etc. I've never noticed comp % being that low in any of my hundreds of simmed seasons.