No current will flow if the ground connection is not attached. You can check all the pos connections and fuses on this car that you want and no current will flow to any of them if there is no ground back to the battery. Check each component you want to test with a jumper cable on the neg side back to the neg battery post. And check it again with a different battery- connect jumper cables directly to the pos and neg leads of the car after you disconnect your battery. You could have internally damaged your battery with a direct short.
Glad you finally found it – it had to be a ground problem like I first said. Electrical issues can be a bear to find – you have to check the entire circuit beginning to end to find the problem and many times visual inspections do not do the trick, you have to take things apart, tug on wires, use a meter to check for continuity, etc.. It’s usually the dumbest things causing the problem instead of something exotic. I bet you’re happy to be on the road again And remember, next time you screw with the battery, remove the neg cable first and replace it last and then you won’t get shorts.