A mediocre team under great pressure can sometimes perform beyond expectations. Bochum is an easy opponent for Leverkusen in theory, people can easily predict the match result. Xabi Alonso chances of leading his team to secure full points are clearly higher, especially since the match will take place at BayArena. I don't think Bochum luck will repeat, unless Leverkusen plays very poorly throughout the match.
Anything can happen in the remaining 8 matches of this season, the situation can change quickly. Leverkusen only needs to focus on maintaining consistent performance. Leverkusen chances of retaining the trophy are indeed low, especially if Bayern Munich can also maintain the point difference between them. However, Leverkusen must remain optimistic until Bayern Munich has truly lock the trophy.
Bayer can now focus entirely on the Bundesliga, they don't have any prerequisites yet to hope that they can defend their champions title, but they have to try to do it, and for that they need to win all the matches, they can't lose points, so even though Bochum is not the easiest team, I expect Bayer to beat such an opponent. On the other hand, I doubt that Bayern will lose the difference that they were able to make.