Ignoring that you can't survive in a vacuum.
If you were to jump of a ledge in a vacuum (in a vertical tube eg). While falling would you feel weightless? Surely the earths gravity is still pulling down on you and you therefore feel your weight?
Now if you travelling upwards on a platform which suddenly stops, and it was at such a speed that you carry on travelling upwards yourself (still in a vacuum) would you feel weightless.
(the thing that I don't understand is why you feel less than your weight when standing in a fast moving lift that is deccelerating, knowing the two extremes will help)