Best posts made by breadandbudder

@droftarts, @Phaedrux, @engikeneer, thank you all for your replies. Turned out to be a faulty heater cartridge. I received a new heater cartridge from an official E3D reseller. It has the correct resistance and is working well.
I suspect the original 30w heater was faulty from the start. When I first got my V6 3 years ago, I think I was only ever able to tune to around 260 and now that I'm printing close to that, it wasn't stable while also pushing filament through.
Also, there is adequate space between the heatsink and heater block.
Glad to have my printer back. Thanks for the help!

@Veti
I figured it out. I feel so dumb.

I had connected the X axis motor to the wrong header. The Y axis is fine. I've been building computers for almost 9 years. I should know by now to check all connections first. I think it's good that I left this problem alone for a month and came back to it fresh.

I'm not sure what happened with the firmware version. I followed along with a guide on youtube from 'Design Prototype Test' and his files.

Thanks for helping! Even if it was to figure out what wasn't the problem.

It's now 6:00 am and all is right in the world.