Electrical gremlins

I have 3 electrical issues I hope I can get help on for my 73 ebody (CUDA). 1) my horn sounded sick but now doesn't work. I was thinking maybe relay or ground issue but not sure. I am thinking check the ground, then check out the relay and third, is the horn the likely culprit? 2) I had to replace a voltage regulator several years ago after it burned up my aftermarket tach. I noticed my amp gauage was pegging out for about 30 seconds every 5 or so minutes. My replacement tach now does not work (has not burned up like the previous one) and periodically the amp gauge fluctuates, no pegging out as it previously had, but fluctuates periodically. Does this indicate the replacement regulator is acting up and needing replacement? 3) The bigger issue; several years ago I lost power to half my dash electrical system, ie, the gauges and several other things did not work. I discovered everything that did not work was on the right bank of the fuse block so I jumped the left side of the fuse block to the right side through a fused junction block that I added. After the issue came about the battery would go dead because there seemed to be a constant drain through the fuse block, even with everything off, key out of the ignition. Jumping the left side to the right side of the fuse block made everything work OK but there is still a draw with everything off that kills the battery. I have to disconnect the battery to keep it from going dead. I was told the issue was the wiring plug that goes to the ignition switch. I bought what I think is needed, a plug that I think plugs onto the switch with wires coming off of it needing to be wired into the harnes. I now am not sure that is what is going on here. I can do electrical but am not great at the troubleshooting part. Any help on any or all of these issues is greatly appreciated. Thanks in advance.

With a jumper wire ground the horn case to the batt neg post then jump 12V from the batt positive post to the horn terminal to see if the horn itself is good. If the sound is weak see if the horn has a "sound trimmer" knob & turn it SLIGHTLY to the right then to the left then back to center & repeat jumping it. If good hook the horn back up & go to the horn relay and ground the wire/terminal that goes to the steering column & see if it honks. See if you have voltage to the relay and continuity from the wire from the relay to the horn. Electronic voltage regs are either good or bad so the reg ain't the problem but make sure it's grounded well. Poor connections anywhere or alt (brushes which are easy to check or poor connection/continuity somewhere inside the alt) or way less likely a bad batt. Not sure where to advise you to start on #3 but www.mymopar.com has wiring diagrams for you but I would unhook the drain on the battery & charge it up and remove the jumper on the fuse box till you get it