Updated the OP with a new version; I am going with the "Pro" skill level...So much more balance between players, especially the WR/DB interaction on "Pro." Obviously the key now is to make the skill level competitive for skilled players. Will see how it works as I have played a few games and have had promising results, though I am far from a Madden champion player.
I came about my penalty slider settings by first noting all penalty categories in the NFL and then associating them with an actual penalty slider in Madden; For example, Defensive Pass Interference also includes defensive holding, for the sake of coming up with a slider setting for Madden's DPI.
So, for example, in 2014 an average of 6.47 Defensive Pass Interference penalties per team league wide were called over 16 games; there were also an average of 6.84 Defensive Holding penalties per team league wide over 16 games....I merely rounded up or down , added the total, and in this case, got a DPI penalty slider setting of 21.
Will it work? So far it is looking promising..This method I am testing does not consider penalty slider effects on game play, as there is a good bit of theory there as it is, and one theory may only hold true if another slider is higher or lower that another slider and so on....
At this point I am trying to input some hard fact numbers into the mix to justify my penalty sliders and see how they test out...
In this case I took that total for DPI of 21 and added from zero...Another option I will try is adding that 21 points to the default slider setting of 50, to make DPI a 71 and so on through all the penalty sliders see how that goes.
My source for the penalty information was from:
http://www.nflpenalties.com/all-penalties.php?year=2014
If you click on the penalty name itself it brings you to a second page that will give the average total per team over the 16 game season for that particular penalty, as well as the combined average of that penalty in the NFL over 16 games.