Was the brake light on all the time due to a faulty brake light switch under the brake pedal??!!

Otherwise, I can't imagine how the 30amp fuse can melt the wires.
Also, I have never seen a 30amp fuse that would fit into the fuse board.

It might be a good idea to find out the reason behind the melting of wires before you replace them. In other words, find the reason brake light fuse to affect the melting of the wires.