you can use this tool
and the known penalties you referenced above to calculate the transition:
So, for example, your A/A 1B at assuming he's historical average and with historical average pitching would transition to 3B thusly:
(.989*.98)=.969 for out of position, and then transitioning to 3B (.96922*.96*.96)=.893 for the moves backwards on the scale. So, you'll have a .893 FLD 3B. If that's better than the FLD of your current D/D+ guy, then go with him, otherwise, keep the D/D+ guy there. Of course, don't forget to factor the normalization into it as well. If he's an .893 fielder from the modern era and your other guy is an .880 fielder from the deadball era, you might want to just stick with the D/D+ guy anyhow. The link above also allows you to run some scenarios to see how many errors each would likely make in different playing environments. I usually use the historic averages for the hitter and pitcher fields and the specific years for the fielders I'm comparing, but if you know more specifically what kind of environment of hitters and pitchers you'll be facing you could customize it better for your needs.
And you can use this tool
to estimate chances (you have to half the chances as it counts both teams in this snapshot).
So, using the example above, your A/A 1B (assuming historical average) at 3B would become a .893 3B and commit 58 errors. Whereas an .880 FLD D/D fielding 3B from 1897 would become a .907 FLD 3B committing 51 errors.