I have never heard of an ECM going bad causing fuses to blow. My guess would be you have a short in the wiring somewhere. I'd start with the trailer converter. If you aren't using it, remove it and tape up any exposed wires.
The key warning beeper is activated when you open the door (if you look in the lower corner of the door, you should see a little rubber covered switch). Usually, this switch just stops making good contact with the body, so that makes the key warning beeper work intermittently. To test to see if it is the switch, leave the key in the ignition, open the door, reach down and twist the rubber grommet/switch back and forth, so it makes better contact with the door jamb. If the beeper starts beeping, then that is what it is. Not really any big deal, if the beeper doesn't work. And it should have nothing to do with your tail/dome fuse blowing.
If you rockers are damaged/dented, it could be possible the wiring harness got pinched and is shorting out. But I kinda doubt that is the issue.
Another thing to check is the connector in behind the left rear tail light. The wires in it are bad about corroding and causing all sorts of issues (although usually it causes the fuel pump to stop working....but you could have some wires shorting inside the connector, causing the fuse issue).
Other than those things, just look around to see if you can see where wiring has been messed with and make sure there aren't any bare wires exposed.
