I seriously doubt he came home and woke up his brother. Using the brother for an alibi.
I don't know what to make of the part about clocking in at 8 using his fingerprint. If he did and then left LE should be able to verify 8 clock-in with Sprint. If he did, then as was pointed out earlier, it narrows the time frame somewhat. If daylight came at around 7 or a little after, I believe that whatever he did with regard to Christina happened between the toll booth and sunrise. Too many chances to be noticed in the light. Between 8 and 1015, EA was probably doing searches on his phone on how to clean his car, renting a shop vac (unless his family had one) and cleaning up the car. I don't believe that whatever happened was premeditated. Therefore, 2 hours is not a lot of time to clean up a car if you don't know in advance what you need, where to get it and how to do it.
Then later he does a factory reset (or multiple ones) to erase his internet searches and any GPS usage between 4 and 7. There are still the pings and other activity on his phone that the company is going to have. I wonder if he didn't turn his phone off some time after 4. If he did any crime he committed might have occurred shortly before that point and that will add to the timeline. I believe whatever happened occurred around 0430 and any cover up not involving the car was done by 0700. Then there is whatever happened to his car to maybe knock time off this period. Again, no premeditation, therefore no planning and greater chance of errors. His damage to the car may even have occurred after committing a crime and caused by nerves and not concentrating on driving. He is going to get caught if he did this.