Not having access to a complete wiring diagram for the truck has complicated the troubleshooting process. It would take a long time to research every possible connection, even with a diagram
, that would cause the problems you are having. The electrical system on 90's on up vehicles are pretty complex, I'm guessing this is why there hasn't been many replies.
As far as your indicator problems, I'm trying to figure out what all the symptoms have in common.
Turn signal/ parking lights and high/low beams are routed thru the multifunction switch for the turn signals, but...
The door open switch goes directly to the GEM (BCM) module. So how this would effect your problem IS the problem in troubleshooting it.
I don't know if the headlight switch goes to that module, seems it would be simpler to just have the switch control relays directly.
If your truck came with a factory alarm, I would imagine it would have all the connections to these circuits also.
They do all have one 100% commonality though- the instrument cluster. The door ajar light, turn signals, high beam indicator are all connected there. Perhaps a ground going to the cluster is bad or non existent? Maybe bad connections there.....
Since a previous owner installed an alarm, there is also other possibilities that the wiring was hacked into at other locations too, perhaps near the GEM / BCM or behind the foot well panels by the doors.
Whats the deal with the Interior and cargo lights staying on?
What is going on with the high beam indicator?
I'm probably over thinking this, I'm just throwing out ideas..... It could be something as simple as the dreaded water leaking into the GEM module problem: