It's interesting as Rüdiger played in the PL and in La Liga during his prime, whereas the other 2 spent theirs in the Bundesliga. International football media doesn't care about the Bundesliga thus no one knows how good Hummels and Boateng were...
No, because Bayern will almost certainly finished top 4 while Dortmund currently sit in 5th. Only if Dortmund finish outside the top 4, so say in 5th, they would win an additional CL spot through winning the CL. Then on top of that comes the 5th...
If Dortmund win the CL but at the same time are 5th in the league, 6th place will also get a CL spot. This was reported in Germany today as it had been confirmed by UEFA.