No, Maniac Magee did not stop and stay in the town of Two Mills because it was the farthest that he could get from his aunt and uncle. He even leaves Two Mills at one point in the story, so it is definitely geographically possible for him to have kept going past Two Mills to another town even farther away from his family.

Readers are told in chapter two that nobody knows exactly why Maniac chose to stop in Two Mills. What we do know is that living with his aunt and uncle had become unbearable, and Maniac chose to begin his running away from them in the middle of a school concert. He started his journey is Hollidaysburg and wound up in Two Mills about a year later.

It should not have taken Maniac that long to cover the 200 miles, and nobody knows why it took that long. We do know that Maniac chose to stay in Two Mills, and chapter two gives readers several theories as to why Two Mills was his stopping point. One theory is that it is just across the river from where he grew up in Bridgeport. Another theory is that Maniac was tired of running and Two Mills was as good of a town as any other. A third theory says that it was the butterscotch Krimpets available in Two Mills, while a fourth theory says that it is because Maniac made a friend early on in his visit. That friend would be Amanda Beale.

Of course, there's the obvious answer that sitting right across the Schuylkill is Bridgeport, where he was born. Yet there are other theories. Some say he just got tired of running. Some say it was the butterscotch Krimpets. And some say he only intended to pause here but that he stayed because he was so happy to make a friend.