Foremost, the 75 player rosters are indeed wonderful.
1 - If I recall correctly from Head Coach 09, contract terms could be negotiated once a bid had been won (at least for user-controlled teams; i.e. there are preset bids in the "auction period"). Someone double-check me on that though, it's been a while since I've played. Or perhaps bids are put in with years on them and some team wants Tony Richardson for three years, who knows.
2 - I don't think releases are taken into account, i.e. Madden doesn't know that the Browns released Rogers before the game started and doesn't care.
3 - I actually do think that Madden AI teams will look for left tackles to play right tackle if they don't see a good-enough right tackle. Someone will have to check me on that.