1. If you don't get any red warning in the output telling you that the FOV range is unknown, the auto FOV feature will use the rounding supported by the game.
2. Monitor Distance is generally preferred.
3. If the FOV is different you can only match one aspect of the sensitivity, and everything else will be different. MDV 0% is generally preferred since it keeps the tracking distance the same.
4. Yes, but make sure you also configure the game with the calculated sensitivity.
5. Some like it, others don't.