He is not a normal teenager. This is a boy who experienced several years of being molested, verbally and physically tortured, and living in fear, pain, and probably shame. He was brought up to fear the consequences of not doing what Michael Devlin said. It's something that's been drummed into him since he was 11 years old. He may have eventually broken free of Devlin's psychological grip on his own, but it wasn't going to happen just because he turned a certain age.
He was also told his mother was killed in a car crash.
I didn't know they publicly announced this information yet (i.e. molestation, etc.). If teenagers run away and rebel against parents who do these things, then why wouldn't they rebel against a non-parent? I think it's more complicated than even this.