Strands of Time by Kris Ruhler

Seventeen-year-old Kallum has life all planned out: pass his simulation test, snap up a job on the upper rung, and ask the girl of his dreams out. No more working at the bakery.
But life has a funny way of ruining plans.
Not only does he get reassigned to a hermit, but his hallucinations also make him fear that he’s turning into his worst nightmare: becoming one of the Crazies.
Worse still, the aetherium, an energy stone bestowed by the alien race called the Aeternas, is failing. And, according to the hermit, it’s all Kallum’s fault. Without the dome shield protecting Levitor, the Reavers and beasts roaming the land outside are bound to invade.
Levitor’s fate rests upon Kallum’s shoulders. But the Aeternas are hunting him down, and he’s running out of time.
What will he sacrifice for the greater good?