If you look to the books that Herberts son and Kevin Anderson wrote... you will find all your answers.. It just took a long.. long... time.. It was a big problem when they fought the machines.. in fact it was Norma who made the Holtzman drive (that doesn't run on spice). The spice is for the navigators. They live off it, and it allows them to see briefly into the future so they don't hit a planet or something.. Anyway .. all of your questions and then some are in the books.. I they are supposedly wrote from outlines left behind by Frank.. The asteroid was a cymek defector and not Tio Holtzmen .. who was a hack that used slaves to make his calculations..Slaves that became the Fremen..