when you call for a single stage from LEO to landing on the moon and back. That approach, known as Earth Orbit Rendevous, was dropped by Apollo back around 1962 or 63 because it was much less efficient than Lunar Orbit Rendevous. Flying from LEO to the lunar surface and back means the lander has to be far heavier than necessary. The lunar lander really needs to do nothing except fly between lunar orbit and the surface. A transit vehicle, functionally equivalent to the CM/SM of Apollo but reusable, would fly between LEO, lunar orbit, and back to LEO.

Likewise, flying straight from LEO to the surface of Mars depends on your mission assumptions. Are you going to go into orbit around Mars first, giving you the ability to wait out possible weather problems, or will the vehicle have to go straight in regardless, hoping for the best. If you're going to enter orbit around Mars, then you'll need to either provide for aerocapture (as yet unproven) or a lot of extra propellant. Will it be possible to make a heat shield that could work for Mars and for Earth (Gary's comments on the Beagle 2 heat shield suggest to me that this is unlikely) or will you be carrying tons of dead weight to the Martian surface?

In short, it appears your numbers are suspect.