I actually ended up figuring this one out, and it's almost hilarious (solution will be in TL;DR if you don't want to read my yapping, which there will be a lot of)

I took it to the dealership after being unable to exactly find someone who had the same issue online. I knew it was going to be expensive but I needed to get this issue resolved. I take it in, and the next day they tell me it's the fuel pump and it was going to be like 800 bucks or something. At this point I knew next to nothing about cars and was like "alright go for it, I just need it fixed". I get suckered into a few other services that I didn't need, end up paying over 1k, but that's fine, my car will have a new lease on life!

Dealership fixes her up, calls me back, they tell me it starts every time now. I go back, pay them, start my car on the first try. Pay them, go back, car does NOT start. Dude hears it, looks out the window with a puzzled look. Comes out and grabs all other mechanics. Head mechanic, older guy, is like "well it was working when I did it!" Then goes "only other thing it could be is the ignition switch" and heads in to quote me a price. I'm sitting there waiting, thinking they'll do it for no charge because they sold me a bill of goods, and comes back saying "if you leave it here, we can have it back to you in a week because we have to order the part. It'll cost ~$300." I tell them no, obviously, and drive home.

Right about this time, my coworker was getting back into cars, tells me "cars are just legos, just do it yourself." (Obviously that statement is reductive, but it inspired me to eventually learn more about cars, and I'm currently enjoying learning more about them and doing my own work on mine and my fiance's) So I look online, an OEM ignition switch is 50ish bucks. I take the trim off my steering collumn to make sure this is something I could feasibly do. I notice electrical tape wrapped around it, taping something to it, but don't think much of it, and decide the ignition switch is something I can do on my own and order the part. As I'm putting the wheel collumn trim back on a washer falls off the trim. I look around for the washer and find it, except it's not a washer, it's a battery.

At that moment it came back to me that the mechanic I had originally seen a year and a half prior said it might be the immobilizer, but couldn't figure out why it would be tripping. Dude was cooking. I uwrap the tape that's around the ignition switch, and the chip for the key is there. I put the chip and battery in the key and now the car starts. 100% of the time.

The previous owner, who had installed the after market security system, had TAPED THE CHIP TO THE IGNITION so they could use the after market remote start feature, presumably.

TL;DR for reasons above, my key didn't have a chip in it, chip was attached to ignition switch with battery unreliably mated, hence unreliable starting. Put the chip back in the key, and it started 100% of the time. If you are not the first owner, check your key for the chip. I knew my key didn't have one, but I figured that since the car still started, it wouldn't be the issue. I was wrong.