You're absolutely right. Based on all we've learned about Steven, I just can't see him with a "getting even" attitude. But then, I'm not sure we really know the extent of the discord between him and his folks prior to his going missing. It may have been more serious than we know - at least to Steven.
Absolutely. There's no more phone calls between them, after the disagreement. Some texts were sent very late at night afterwards, but went unanswered.
What we know about him, is primarily from his family.
We've had some insights from at least one friend, which told us things that either the family didn't know about....or didn't want to mention.
I may be very very wrong, and this applies to ANY case: the most important clues, may be the "absolutely very worst things" someone knows about the missing person ...and maybe those things have been shared with LE and the PI. Those things are none of the public's business - nor ours.