Q: My car has no electrical power and there is a blown 80 amp fuse under the hood

drove to school fine, after class i went back and nothing worked absolutely no electrical, but my battery is a week old, newly purchased from Costco. after unscrewing the connections to the battery and then re-screwing it my car would turn but not start. i tried to jump it with a friend, after connecting my positive to his batteries positive and my negative directly to his negative we waited 30 sec and tried it but no start AND no turn.

we saw the fuse blew (80 amp) (all other fuses were fine even the under dash ones)... for a quick fix we jury rigged the fuse to connect to itself (pressing the blown pin inside the fuse back together) and we got a turn BUT no start, then finally we directly connected his positive to mine and his negative we connected to my frame, to ground it, miraculously it turned and started after like 3 sec of the key in the start position.

My car has 160000 miles.
My car has a manual transmission.