Historical Sim Question
 

If you use the option to have a players' fielding ratings set by each season's real life stats, do the ratings change at all in season? Say I have a player who played mostly left field in real life but also has ratings at right field. If I play him at RF all season does his fielding rating go up due to more playing time there?

Secondly if I play a player out of position would he eventually get fielding ratings at the position I play him at?

Yes, no matter what you choose, as long as you have player development ON, they can learn new positions.

In that case would their rating the next year be based on what they played in real life that season or a progression of where they left off the season before?

This.