Read my guide =p
To answer you first question, on D-league stats are very random so I would look for playing time over anything. I actually play my d-league players on relaxed to maximize playing time to get as much XP as possible.
As for SAs, I would strongly recommend bringing throwing, vision and strength to the 48 cap before putting any SPs anywhere else. For the most part you are going to be sharing time in the dleagues and on the 13 capped leagues, so stam is not really a huge factor. The thing about moving the three main attributes up to the first soft cap is you get .40 of a point in each of those per level, where if you spend early on SAs they don't naturally improve. Soft capping the main attributes early with give you a few more SPs in the long run to put other places, making your QB stronger down the road. Also for the most part, SAs work as attribute modifiers, so the higher the attribute it modifies, the more benefit you get out of them.
