So you have a short in the system or you wouldn't be blowing fuses. Also visualizing that you have a wire going from the battery to the frame and doing a voltage drop test does not guarantee that you have a good ground as that can change at high amperage. You should remove that wire, scrub the contact points with a wire brush, and look carefully at where the wire is crimped to the ring terminal. You can also diagnose whether ground is an issue by running a wire from the starter mounting bolt directly to the negative battery terminal -if that fixes the problem you know it's a ground issue. Do you have a wiring diagram you can post?