Braun had less than one year of service time. Fielder had over 2. Fielder felt he got screwed over the previous year when instead of getting a raise above minimum, he just the raise that all players making minimum got. Context matters.
So dump him when you actually have someone better. Jackson is a left handed 25 year old pitcher. He's unlikely to be more than a reliever but he's far from the cut bait point. The Brewers have two open spots on the 40 man as it is and can move either Capunao or Gallardo to the 60 day to free up more room.
Yost pretty much gets to determine the last few guys on the roster from everything that seems to be said. Since he's the one that will use them it makes sense.
Because he hasn't done well this year and has never done well before. He's a career 6 ERA pitcher. He has walked 11 batters in 15.2 innings this season.
The point is that he only skill that Gwynn has that isn't duplicated on the team is his speed. If you are never going to use him to pinch run than get a real bat up here.
Ypou know why people focus on the managers to a great degree? Because the stupid broadcasts spend 2/3rds of every inning talking about how great and important managers are.