Hey, so figured I'd share an update after today's vet visit.
So the vet is fairly confident that it's not septicemia, and that the first vet (the one in my home town) likely just completely misidentified things. That being said, she did agree that the other symptoms were some cause for concern, just not immediate life or death concern. The plan was to draw blood for tests and send me home with antibiotics to give him over the next month, but they were unsuccessful in drawing blood, so the new plan is to start the antibiotics and monitor him closely over the next month. I may or may not (depending on how he responds to the antibiotics and better managed heat) bring him back in about a week and a half to try for the blood draw again.
Either way, I feel much better just knowing its not the one big bad thing. Still unsure what it is, but at least I have the time to find out now.
Thank you again for all of your help! Likely won't reply back today if solely because its been a very exhausting day, but I will still be around in general, and I'll definitely keep y'all posted if anything happens <3