re: 2 spacecrafts
yes, keep the lander going between the fuel transfer station in lunar orbit and the surface - no point in carrying that mass to the Moon for each landing -
As for CEV failure on the way out, the fuel transfer station provides another abort location - remember also that it has docking capabilities, it CEV docking system is down for any reason -
the loop of the Moon and return is available as well as an abort option, as for Apollo 13.
ep