im a sparkie and reverse polarity is not a good thing, i think the ecu may be fired as it keeps blowing your fuse. i hate to be the bearer of bad news but i think the repair bill is going to be hefty. i know for a fact but stereos dont work after conecting them backwards, dont ask me how i know but as you turned the key with the battery backwards everything in your car has seen reverse voltage, so anything with electronic in them are probably buggered, hopefully you did not have a cb or anything too.

i would first pull a spark plug lead and see if you still got spark. then see if your fuel pump still operates.

hopefully someone else chimes in and its an easy fix but i think at a bare minimun your up for a new ecu.