The plants are about 2' tall. They are from some low grade stuff I had a while ago. The males are really easy to identify, boys=balls girls=buds...lol
Is 30 feet far enough away? ? and forgive my ignorance but why collect the pollen?
As for clones, I am not confident enough to cut clones yet.
If they are from lowgrade stuff there is no use keeping them. Collecting the pollen would allow you to pollinate your females and make seed, or you could just leave them and it will happen naturally. However, the poor genetics are not desireable at all so I would advise just killing them unless you are really desperate for more seed. If your only objective is to grow the females to smoke then kill the males, pollination will reduce potency and yeilds.
MJ plants uses the wind to spread the pollin and you would be surprised by how far it can travel. If you want seeds, leave them, the closer the plants the more seed it will produce. If you want bud, I think you know what you have too do.