The reason why i switch back to "0" is because a lot of people were saying their 3rd string QB was throwing for 70% completion in the passing game. I also was testing this out in one of my 2 games. I took a QB: FA rated 58, and stuck him in a couple of games with default sliders. He was throwing for 280 to 320 yards with a very high completion %, and he didn't even know the playbook yet.
I've been finding the "0" sliders for me work well as you can see from my season stats i posted before. As for the FG, at default and on "0" my kicker would always fall short, but at 95/95 he can have the distance.
This is what i do when playing these football games. Try to get a realistic game play. It's hard because you want to make sure a good QB is good most of the time, and at the same time a bad QB is bad. I don't want sliders that allow a good QB and a Bad QB all be good. Then you might as well have your 3rd string QB be your starter.
Do the test yourself, take a low rated QB and play him, and use the default sliders. Let me know what his stats are. I suggest to play atleast 2 games in career mode.