Well, it will be a tough schedule for Stuttgart and I'm pretty sure they will fight it out in these three matches. They must at least not lose a single point and if necessary Stuttgart must hold on to a draw rather than not scoring any points at all. The toughest challenges for them are against Bayern Munich and Leverkusen, but against Dortmund I believe they can take 3 points.
The job will be even more difficult because they have to compete with these teams at the top and the condition for them to be able to maintain their current position is not to lose. Maybe on the other hand, if Stuttgart loses the match against Bayern Munich and Leverkusen, then Dortmund has the opportunity to shift them from 3rd place in the standings.
Three matches can certainly be a stumbling block for Stuttgartf this season in maintaining their position in the Champions League zone, but I think they will be able to get at least 7 points in those 3 games, I don't see if Munich and Dortmund will be able to prevent Stuttgart from being able to get 6 points in these two games, currently the performance of Munich and Dortmund is no longer as great as last season and besides that the busy schedule between the Champions League and The Bundesliga certainly has to force them to choose one as the main focus this season, the game against Dortmund has a short span between the Bundesliga and the Champions League so I think Dortmund will not risk fielding many main players in the game against Stuttgart later.
The only difficult match for Stuttagart may only be Leverkusen, so far Leverkusen still has performance and consistency in winning every game, but there is nothing wrong for Stuttgart to play optimally in that match at least to be able to get 1 point like they did in the first Bundesliga match of the season against Leverkusen.