Mara cannot destroy enlightenment, if he could it wouldn't be enlightenment. If you were doing a Goenka 10 day vipassana course then the idea is not to empty the body of sensations but to fully feel sensations. Where did you get the idea that Mara will come and harm you in your sleep? I think you are worrying about things you needn't, Mara I think is most probably a personification of our own delusion not a separate being. It's not uncommon for people on intense meditation to be lucid for periods of sleep so I wouldn't be surprised if the Buddha was much of the time