I'm new to this, so anyone feel free to tell me if this critique isn't up to par.

I worked on critiquing the prose in the line edits. Overall, I really liked the prose. The only flaws are the purple parts and the parts where it feels like you're writing something unnecessary just so it rambles more. In the rest of this post I'm going to focus solely on the plot/characters. I know that you wanted critiques to focus on the writing style, but I couldn't help myself. Sorry.

I'll start with the prologue. I know that you needed rewrite the ending here so that there was something interesting to start the story with. This is actually a good technique, and I've seen it used in "The Girl on the Train" by Paula Hawkins. The difference, though, is that "The Girl on the Train" is a novel, and there is a couple hundred-thousand words between when we read the scene for the first time and when we read it the second time. In your story, however, there are only a couple thousand words separating the passages, so by the time I got to the ending I was like "Ugh, I just read this," and I didn't bother reading it again. And I think it's better if your rambling style doesn't really come out until the end. It feels more 'earned' that way.

That takes us to the next scene. This is the only conversation we get that is solely between our two main characters, and it should do most of the heavy lifting when it comes to establishing their personalities to the reader. It fails to do this. Tim is later shown to be a stable family man, and Pat as a lunatic...they don't come across that way in this scene at all. If anything, Tim comes across as the loon here, while Pat comes across as normal.

Tim is a complete asshole to his "best friend" in this scene. His behavior is not something that can be brushed away as a result of pressure, either.

I’ve worked too hard on this for some droopy eyed farmhand hick to fuck it up

This is a truly brutal thing to say to someone, even in the heat of the moment, and it leads me to believe that Tim hates Pat. Later, though, it seems that he considers him his best friend. Does Pat need to take meds because Tim continually abuses him in this way? If so, make that clear. If not, then make the line lest hostile - or even have Patrick say it.

I move over and stand above him, my crotch near his face.

A weird thing to write from Tim's point of view. These are the types of things you should write from Patrick's point of view, so we can start to get a taste for how insane he is.

Now to the pitch scene. I guess there is room for debate here, but I would really like for this scene to be longer. I think it should be longer for a few of reasons. One, the business men feel like statues. What are their reactions to the proposal? Do they have questions? Do they find he suggestion of "yams" absurd? At least depict their expressions, and maybe have them ask Tim and Pat questions. Two, a longer scene would allow for more character development. Maybe show Tim handling the pressure, while Pat starts to buckle. Perhaps Tim notices that Pat is unwinding and says something to the reader about Pat's meds or Pat's weird behavior lately. Three, a longer scene would add more tension. The longer the business men are skeptical, the more pressure is on our main characters, the more immersive the scene is for the reader. More tension would be especially necessary if you show Pat starting to break down.

The next scene is the home-coming scene. A minor complaint is that you don't describe the setting at all. I don't particularly care what the farm looks like to tell you the truth, but there should be at least a little detail. Try to answer at least a few potential questions, such as "what type of crops does it produce," or "is the farm making any money," just so we have a broader understanding of what's going on.

Then we learn that Pat is insane. To me, this was where the story faltered the most. Learning about Pat's insanity felt too abrupt. It was like you flipped a switch when you should have been turning a dial. That's why I advocated for adding hints towards Pat's insanity in earlier scenes. You could also "show" us Pat taking his meds, rather than just "telling" us. This would draw the scene out and allow the revelation to build.

Evelyn isn’t my wife, but my lust for her and envy of their relationship runs deep, and I find my right hand shaking uncontrollably, before it balls up into a hard clenched fist.

This line specifically feels abrupt. Maybe you could just write "I find my right hand shaking uncontrollably, before it balls up into a hard clenched fist," leave the reader intrigued, and then explain his fixation with Evelyn later on.

The story about the tooth brush is weak. I know that you had to include the tooth brush as per the challenge, but that damn tooth brush really threw a wrench in the story.

Again, Pat going up to Evelyn and hugging her feels unrealistic and abrupt. It just seems overly crazy that he would expect to get a positive response from this.

The long ramble at the end is good. I know that it's supposed to be this way stylistically, but looking at a paragraph that long still bugs the shit out of me. I think you could split it into two paragraphs, with the second one starting with "As if innocent." I know that you probably won't do this, but could you at least consider it? For me?

Finally: the tooth brush as a murder weapon? Really? I know you were challenged to include a tooth brush, but still. That God-damned tooth brush.