re: CEV and Moon flights
Separating the CEV from the Moon rocket does make sense as it leaves the possibility to use the CEV for earth orbit missions and it reduces the risks around the HLLV.
The thing is to perhaps first launch the unmanned HLLV before the CEV and waste as little time as possible in LEO.
Also, a bigger LM would be able to return back to the CEV even when its orbital path doesn't match the moon landing site.