Here's my take from a male perspective:
There's no reason to suspect insurance fraud on the car. A 2003 Cavalier isn't worth much and he still owed on it so he did have to have full coverage. Probably owed about what it was worth, just a guess.
If he left for Las Vegas the night before he may have met up with someone in Vegas, maybe someone that worked until late, we will call him or her Person X. Maybe even GW saw him with Person X, who knows. This would account for the clothes that don't look slept in and the clean shaven look, Person X may have an apartment or house in Vegas.
As for that neighborhood, I don't think the car was there randomly. I also don't think he went there to visit someone who lived in that neighborhood. I think Person X has family there, parents or Grandparents and they attend church or brunch together every Sunday. Person X does not want to bring SK along, at least not yet, so Person X says meet me near where my parents/grandparents live. Park down the street, I'll pick you up at noon and we'll go do whatever. It saves Person X a trip back to Vegas so they have more time together.
I think the trip back home may have been for something like the passport. It would be needed for a job or a NV license. Or SK could be working under the table for cash like before.
Now, why would I think he ran away? I think it's similar to what happened to Nicholas Francisco. NF probably felt trapped because there was little money and he was married to a princess (every thing about the wife leads me to believe she was high maintenance). Finally he had too much and left.
I think SF may have felt smothered by his family. When things are good, that's fine. But the earlier jobs he had were closely related to his father and his family is now deeply into his financial troubles. I don't mean this in a bad way, it's obvious they were trying to help, but SK may have felt trapped by this.
So he meets Person X again and they start talking. SK decides he really has little use for a car he can't pay on, so he just leaves it. And with nothing much else to walk away from, and the new life looks so much better than where he was... And somehow Person X does not fit with SK's old life.
For whatever reason, Monday he dials voicemail and that's the final break with the old life. Personally, I think there's a TracPhone or public computer use somewhere because I don't think any of the meeting was random. I do think the odd driving everywhere first was random.
Just my thoughts.