weird guys!!!! My first response would have been, yes replace the mega-fuse! BUT it is also conceivable that you have a bad cell in your battery or a short. The other things to do is to check all the wires coming from the alternator to see if they are loose or are cracked.
You have a system, my recommendation for you is to take the fuses out of the system first so that your amp is out. Then try it and see if the amp is pulling gobs of current. Also, check your terminals on the battery itself. Remove corrosion and see what that does. Going back to the alternator and the terminals, make absolutely sure they are tight and all the snaps are engaged FULLY.
Keep fighting, you will get this fixed soon! Be sure to post what failed so the rest of us can have that info!!!!
Thanks
L8R
Rich