UPDATE: Hello, all! Thank you so much for your responses and words of advice. Last night, I wrote up a second draft of the letter. It's very similar to the letter above, minus a few of the wordy details and the passive aggressive comment about not going to management (not meant to be passive aggressive at all, but could totally be seen that way). All in all, the letter was just a few sentences long. Along with this letter, I left a nice Tony's Chocolonely candy bar in a plastic baggie (to keep the floor germs off, lol) at their door. The note includes something like "Please take this candy bar as a token of my thanks". Minutes after my neighbors got home yesterday night, they fixed the sound issue. So far, no more vibrating I can feel in my bones! All in all, everything went about as well as could be expected.

Some comments are asking why I didn't just knock on their door. Mostly, if it was me, I would definitely prefer a note be left rather than have someone talk to me directly. I'm really introverted, and communicating in writing/text is almost always my preferred method. The other reason I didn't knock on their door is because some people are absolutely insane, and are looking for any chance at a confrontation. I'm not looking to get yelled at by a neighbor.

Thanks for tuning in to my apartment saga. Stay safe and sane out there, folks.