How did Olson's group manage to rebel against Babcock's influence? I thought everyone in Haven had completed the dream sequence and become thralls.
They were under his influence but not under his control. Babcock left his foodstock mostly alone. Though he states that he's dominated everyone he telepathically contacted, presumably he was talking about the people in the prison, who he'd use as his guards and governors, and not the general populace.
Otherwise, giving in easily would probably give you more mental freedom then if you resisted and had your mind assaulted and broken, since everyone shows evidence of being "touched" by Babcock but have varying levels of independence.
First Colony is a hastily assembled, sustainably defensible settlement in California, settled primarily by refugees which are brought there in an terrifyingly dangerous train convoy where most of the cars are swarmed by virals. Why not populate First Colony with refugees from the West Coast (things must not have entirely broken down yet, since there was enough organization to build the settlement), or build it on the East Coast? Or have multiple colonies? Surely it would have been easier than putting together a transcontinental rail journey under the circumstances.
There *were* multiple colonies, but most of them succumbed before the events of the book. A reference is made to a Taos colony which got overrun, and it was mentioned in diary of Ida Jaxon that there were multiple trains from other cities going to different places (California and New Mexico are mentioned).