Good point. I think I recall reading about high-functioning opioid addiction as well. That, too, would make living on the run difficult.
As far as other notions Robert Fisher started a new life, I think it's easy to get caught up in quixotic depictions in film (
e.g., character with ready passport/envelope of money in a safety box, becoming a "Jason Bourne" at the drop of a hat), but real life is a lot more complex. A prolific fugitive requires stoic adaptability and resources, not to mention planning and time (which Fisher didn't have). While switching vehicles in the middle of the wilderness would have been an expert strategy, Fisher was hundreds of miles away from an airport or border (and after leaving Scottsdale, even farther away from Mexico). Also, what vehicle? Did he have one hidden underground with a fake name on the registration? Did someone (friend, old Navy buddy) pick him up after ditching the RAV4? Why? What was in it for them? Why wasn't the person(s) not disturbed/curious when local news reported on the murder of his family? And assuming seasoned law enforcement questioned every Fisher family acquaintance - how would the theorized "accomplice(s)" bypass questioning or fall under the radar?
Finally, speculating Fisher ended up beyond the border (and found a cheap doctor/clinic to feed his addiction) wouldn't a much-publicized $100k bounty be a better windfall than whatever he was paying them?
My case rests for now.