1. EA says they fixed that this year and now the in game overall will match the menu overall (the scheme overall)
2. To be honest I am not sure how overall affects the simulation engine. I remember you (at least I assume it was you) mentioned the Hester thing before but I never noticed that problem so I cannot speak on it.
3. Front end overall is the default rosters that are used in play now. They are the "true" overall. Your trick of changing scheme would not work for two reasons: Once a AI team makes an offer your lowball offer will get declined.More importantly, your scheme does not affect the free agent's asking price. His base overall determines how much money he wants.