No comm ecu, no power in aux but do when key turned forward,

I am having an issue with a 2001 Ford ranger V6 4.0L sohc it started when we were driving down the road the truck would start jerking and the gauges on the dash started going haywire and then and I pulled over and the alternator wire was cut so I spliced it back together and managed to get the car back to the house I took the alternator harness off the car and replaced the alternator harness with one from a junk yard I also replaced the battery because I have had lots of problems with that battery needless to say I put the new harness on and when I hooked it up to the battery's negative cable it sparked and started a fire knocked a chunk out of the battery and brunt up the fusible links. I replaced the fusible links and hooked it up again and it didn't catch fire but it burnt up the fusible link again. So once I check the wires and discovered that the wires on the harness were pinched between the alternator and showing wires so tapped them up again I replaced the fusible link replaced the alternator when I hooked and this time when I hooked up the battery cables the fusible link didn't burn up but when I went to go crank up the car I turned the key on on the lights came on but when I turned the key to start it or crank it nothing happened I took a screw driver to the starter to try and jump it and it attempted to start but wouldnt when I turned the key to the aux position I get no lights on the dash only when I turn it over tho the run or start position. I tried to plug in my obd 2 and it tells me no com with ecu. Used two different OBD2 readers same thing when I sprayed starter fluid and the jumped the starter the truck cranked for a second but I heard some weird horn kinda sound that I never heard before and I still have no lights when In aux but I do when I have it in start but nothing when I try to start it unless I jump the starter