It would be easy to find a scale since they show you what ranking that player is among the nba, so just finding who the top ranked guys are and give them 99 or close, and then the absolute worst bottom guys on the ranking and give them a very low, and scale from there while only rating guys with at least 100 possessions defended.
(For example make a mix between whatever is iggy/LeBron/Dwight's overall Opponent PPP and Opponent FG% into a 99 for on ball defense)
From last year's numbers when I checked at the end of the season, the absolute top defenders had around 0.69 PPP given overall, and around 35% for opponent FG% (A mixture of those 2 would add to 99 on on ball defense, and the farther it went from them it would lower?). and the Amare Stoudemire's had 1.01+ PPP given and high 40's FG%. The problem is as of right now you can't check last season's ratings wich would be a great accurate representation. At least on free version I can only check current season data, wich is a very small sample size and has crazy data (for example Tony Allen hasnt been very good so far even tho we know he is a spectacular defender), so it's probably better to wait some more time in order to change those.
Same for Post PPP given and FG%, wich would directly translate to the in game rating of post defense in a similar 0.6-1.1 PPP given, and 35-50 Opponent FG%.
Defensive Awareness couldn't and shouldn't be updated based on this, since theres no stat at all that quantifies it (help defense/rotations)
I don't have the guru version of reditor, is it a paid one?. If such is the case then sadly I'll never be able to fulfill my wish, since I can't afford to pay for a tool just to update my roster. I will be forced to wait and see if any caritative soul ever wishes to do this.