cpspalding read the link below. It should help you with some GD facts and help you along your way.
https://www.whatifsports.com/knowledgebase/KB_Article_Details.aspx?kbid=674
This happened to me when I was new so I feel your pain. I think it takes 3 games of promised starts to have your WE improve. You'll realize this because the player will send you a letter saying thanks for keeping your promise. You must keep those promises or it will come back to bit you again! In addition your WE will increase but expect it to be around -5 or -6 from the original WE. You can slowly recover more by giving them extra playing time during the season.
Here are a few thought on playing time for your scenarios.
QB - Your SR at 85% and Sophomore the same during the first half. You want your better QB to hopefully give you a good lead before the second half. Then your Soph at 95% and SR at 85. This should get you that Start.
LB - Make him your 4th LB in the first half so he gets some playing time. Then in the second half make him your 3rd LB but adjust him to 95%. Keep playing with those number and you'll find what works for your team as you gain more experience.
All the best!
Talonino