I have been to Dachau Memorial, but, quite frankly, I wasn't looking for a taxi stand. Can't help you there. I don't see anything about getting there by taxi (only S-Bahn/bus or private car) on the Memorial website.
The bus from Dachau Bahnhof to the Memorial takes 7 minutes. After it lets you off, it loops around and returns to the Bahnhof 11 minutes later. So if you board that bus at the Memorial, it will take 11 minutes to get to the Bahnhof.
There is a taxi stand at the Dachau Bahnhof. I don't know if it is continuously manned, or not. There is probably a number posted to call, but do they understand English? How long would it take for a taxi to get there. Google Maps says the fastest way by car takes about a half hour.
According to the MVV-Munich website, there is a 59 minute connection from the Memorial by bus to Dachau Bahnof, by another bus to Moosach, then by U-Bahn to the the Olympic Center with a 4 minute walk from there to BMW World. There is a bus from the Memorial every 10 minutes. You could leave the Memorial at 10:56 and be at BMW World at 11:55 (Olympic Center U-Bahn station at 11:51).
There is another connection (66 minutes) which goes by S-Bahn from Dachau station to Marienplatz, then by U-Bahn to the Olympic Center. If you left the Memorial on the 10:46 bus, you could get to the Olympic Center station by 10:48.
