You probably have to take an OC job at a bigger school first. I have two success stories for you.
1. I started as OC at UAB. There for 3 years, then hired as OC at SDSU. There for one year, hired as OC at Mississippi State. There for two years, hired as HC at LSU. There for 3 years, hired as HC at Notre Dame.
2. Started as OC at Navy. There for three years. Hired as OC at South Carolina. After one year, Spurrier was fired and I got promoted to HC. After 5 years as HC at South Carolina (2 NCs), I was hired as HC at Auburn.
Just stick with it. If you want to become a HC within a few years, you probably have to start as an OC at a 3* or 4* school.