How old are these kids? I wasn't sure so it threw me off a bit.
I feel like, in terms of realism, the biggest thing you need to change is your dialogue. Even from the first line: "Jesus Christ, give it up Truman, you’re never going to find bigfoot.
You never even saw him in the first place" it just feels really forced to give us as much information as possible. Same with "What really happened that night, Truman?" The first thing I thought about when I heard that was rape.
You don't describe Bigfoot the first time he is introduced, which could help.
I find it weird how they conveniently fall asleep in the woods. Truman just sits by a tree and falls asleep. I mean, if he really believed Bigfoot was out there, why would he do that? It's mid-afternoon, how tired can he be? Furthermore, you don't specify what time of day it is after that, so it left me confused how long he'd been asleep.
And this happens again when Bigfoot is right outside there car. I can't believe that Truman can fall asleep at 7 o clock (and sleep until 6 am) just hours after he's taken a hefty nap in the woods while a monster is right outside his car after he and his friend believe that they are going to die. Does this mean Bigfoot is using some kind of sleeping gas or something? You can't go from "Roger: We're going to die / Truman checks his watch / They both fall asleep."
"They battle for approximately 20 seconds." Well what do they do? It doesn't seem like a fair fight, so write it so.
And why would Truman get mad at Roger for killing Bigfoot. Wouldn't complete disbelief and shock be the more believable reaction to finding out it's his father? Then why does Roger shoot himself? It seems like he wants to live very badly, but then makes this 180 because he fought in self-defense against his clearly psycho friend?
As for pacing, there's no real build up to seeing the Sasquatch. We're not even sure he's real until he just pops out of nowhere molesting Roger on page 8. I don't think the dream sequences help build that tension. Maybe instead of dreaming about the lair, Truman can actually find it after he's separated from Roger. Then when he goes back, he'll find Roger gone.
The story is confusing. I'm not sure if it's a comedy or a horror. And it doesn't really make much sense how his father would think dressing up as Bigfoot would be the best approach to molesting kids. There's a couple of forced moments like Truman finding a gun in Roger's house or Roger spraining his ankle which make it feel less natural.
As for formatting, I think you can do away with the CUT TOs. I've been seeing less and less of it, and I'm not sure you need it. Your action lines can use some breaking up. Large blocks of text are intimidating. Sometimes it's a little wordy. You use a lot of "begins to" "starts to" or "is running" and a lot of it can be cut to just using the verb. "Truman pees, Truman Runs, Truman walks."