iMac All Kinds Of Boot Issues

Howdy, I bought a used Late 2014 iMac 27” 5K back in July 2021 pretty much solely to use for Autodesk Fusion360 and Cura for 3D printing, plus I installed Windows 10 with Bootcamp. Everything was fine and fast as ever on Mac and Windows until around October. It got unusably slow suddenly. Like literally overnight, and I just got annoyed, shut it off, and didn’t touch it until recently. Well I need to design a part for work, so I fired it back up, and it’s even slower now. 5-10 minutes to type in my password on startup. Not to boot the desktop, just to type in my password… So I uninstalled everything that wasn’t Fusion360 or Cura. Then I went through Bootcamp to uninstall Windows. Everything seemed to go fine. Once the “Windows successfully uninstalled” message popped up, I closed out and hit restart just out of habit. Now it refuses to start up. If you just try to start it up like normal, it will go to the Apple logo and will load to halfway then freeze. If you start with the Options keys pressed, it will open the page that has only Macintosh HD on it now since Windows is gone and it will give me the option to pick a network. If you hit the MacHD, it will pop up a error “there was a problem, press any key or wait to restart” and then will start up to the Apple logo until halfway loaded. I tried to start into safe mode with Command+R, it will start into a black screen, and never even makes it to the Apple logo. I reset my VMRAM and that seemed to go through the process like it should’ve, but didn’t do anything for the startup process.

I’ve looked all over trying to find somebody with a similar problem, and everything I found was “I started in safe mode and it fixed it” or “I reset my NVRAM and that fixed it.” But nothing with my issues here.

Thanks!

BP67