That logline needs to get to the point...forget the first half and keep the second. As the script itself is concerned, I'll fess up and say I was cutting you a lot of slack- but I threw in the towel at p50.
It wasn't due to the old naming characters after horror directros that took me out. It was Rex. Rex does not have to be a nice guy. He does not have to be a good guy. He's just overwritten.
Some of the cult happenings past and present could make some good horror; visions of teacters getting taken over by demons and tormenting Thomas can also work I think. But you stack the deck against Rex. I don't care hat happens to him, he gets what may be coming to him. While the early scene with him and Rebecca under the stars is long and at times OTN, it's far better than the one previous at the outdoor cookout. They are in love, he calls her a cunt not once but twice; there's a unneeded and inappropiate joke (?) about the late Micheal Jackson.
A few years later, sometime after Rebecca's Rex is abusive to his son; we also find out he is a racist. (Although I read it as another attempt to make him more of a sleazeball when he is already set up as a sleazeball--it's almost as if you want to remind me he's a sleazeball) Then he gets into more rants and stuff, and instead of being threatening, he comes off as an over the top stooge. I try to focus on Thomas then. Too bad the kid is passive.
Then I noticed tech issues more (I let some early intros with characters uncapped slide...but after I saw INT. EXIT on one page, that was it) and inconsistant bits of dialog- sometimes the characters would have the intentional mispelled dialect; sometimes not. Word of advice: don't overdo that. You could make a reader either view it as spelling errors due to flip-flopping, or worse, you tell spell check to know that spelling.---and there WERE spelling errors in the narrative like that, bad use of pronouns, (he, she) and wrng use of subject shots that made the read awkward.
There was nothing for me to hang my hat on. I started to like Rebecca early, but she turned into cardboard and you ditched her shortly after her big announcement to Rex, who called her a cunt earlier that afternoon. I dunno, maybe it's just me, but I'm surprised she didn't slap him or, after telling him the news, pack up at move to Milwalkee. Y'know? He's a sleazeball.
I don't know if you're sticking around. But the piece needs to be more tight. I was kind of let down as the script progressed. There needs to be some rules around in here that you can't break in the work. Not a bad attempt though for the most part.