Just a little nitpick here
1 million colonists take up 5kT of space. Now, kT means kilo-Ton (I'm going to be using english system, since the nitpick is on "right now 100 (colonists) weigh only 1 pound!"). One ton is 2000 pounds. Thus, a kilo-Ton is 2000000 (2 million) pounds. Now five of those makes 10000000 (10 million) pounds. Thus, it's not 100 colonists weigh 1 pound, it's 1 colonist weighs 10 pounds.
I realize that this is still pretty tiny, my little dog weighs 15 pounds right now, even if she is spoiled and obese.
I just wanted to nitpick
Oh, and before someone nitpicks me on this, I know I shouldn't have used the term "weigh". In space, they should weigh nothing because they are only in the presence of microgravity. I meant "mass" for everything, ok?