Without diving into how bye weeks could affect certain games, I think 6.5 for USC is about right, tbh.
Two sure fire losses on the road to UW and ND, probable losses to Utah, Oregon and Stanford at home, and then toss ups/slight SC favorites vs UA and UCLA at home and CU, ASU and Cal on the road. Fresno State at home in week one is surely a win and I don't really know how BYU is supposed to be this year, but they travel to Provo, so I see as a toss up/slight SC favorite matchup.
For them, I think a lot depends on how they handle the first 4 weeks. 4-0/3-1, and I think they have the confidence to keep playing well for Helton and hit the over. If they go 2-2 (which I think it likely) heading into roadies against UW and ND, I think they come out 2-4, with an apathetic attitude and things probably snowball from there.