A multimeter would help a lot at this point.
Including the in line fuse, it could have blown other fuses
Or links.
I hooked a battery backwards once. It had all kinds of problems.
It could be a few things, but checking to see if the battery is receiving anything from the alternator is first.
Power regulator, positive cable, links, engine fuses, check both fuse boxes, and more.
A direct short is said to waist a weak battery, I've just never seen it.
Electrical troubleshooting is always a pain, more so in newer vehicles.