The Rule
Expertise Is Bounded By Lived Hours
A character cannot realistically know and have expertise in things that require more hours to learn than he has lived. To attribute them with abilities and expertise beyond what is possible in their lifetimes is to invite reader disdain.
Commentary
Watts is Cline, Cline is Watts, and the fact that Cline spent his 40 years immersed in a culture is not something that translates to a teenager with five years of solid study, no matter how intense, being able to duplicate (barring some special talent, which Cline pointedly demurs from gifting Watts).
Cline repeats this error later on when Wade is working ten hours a day, but also playing, researching, gunting, etc.
A single pass-through of all most of the material listed would take a year—but we see Watts' day-to-day life in the book, and this all "stuff he's done" without ever being "stuff he does". We see him going to school (which he graduates), climbing around his trailer stack, and hanging out with other culture-obsessed "gunters". Oh, and the week he spends pleasuring himself which, if we're being honest, we know can't be the only week he spent that way.
Oh, also, he's a pudgy, mal-nourished, non-light-receiving, sedentary teen living in a post-apocalyptic world, but who has the idle time and physiological wherewithal to absorb all this, which is a species of Trucks Carrying Goods and Workers.