All great questions and points, Milopede!
To answer your question about what number the 911 call came from..I believe Chris called 911 from his cell phone, as he was leaving the gym.
I COMPLETELY agree with what you're saying about if he left at 5:30 am and called police at 7am..that only would leave the perp (assuming it's not him) about an hour and a half to commit the crime. Also, around 6-6:30 or so, I would think some of their neighbors would be up and leaving for work, or at least awake. I wonder how come no one reported seeing a strange car at their house, no highschoolers going to school (i know most highschools start around 7:15ish..so I would think they would be up and on their way) saw/heard anything, etc. It just seems weird that, on a weekday, the neighborhood was completely dead in the mornings.