Fuse panel- red wire that is in IGN slot goes through firewall to engine and not sure where it goes.

This is my brake switch with orange and white wire with white wire spliced with a red wire and red wire is coming from my trailer brake box
I have a 91 full-size blazer. Had a aftermarket stereo installed. Brake light went out so I change the bulb.then fuse blew for headlights. I changed fuse and had friend who installed stereo come and fix stereo. I don’t know what he did but the stereo was working. BUT without keys in ignition I step on the brake and not only do they come on but my running lights, dash lights, dome light, license plate light, and buzzer (that buzzes when leave keys in ignition) also come on.
with the keys in on position the left blinker is fine but when I flip to right blinker it’s like I turned hazards on and all blink.
Also something is drawing power from battery and draining it.
So this is what I’ve done: changed brake light bulbs, front running light bulbs, brake switch under dash, headlight switch, found melted wiring underneath rear wires that I fixed and none of it did anything. I unplugged the brake light switch plug with white and orange wires - the white wire has been spliced with a red wire coming from the trailer brake box. When I unplug that no brake lights but my rear running lights still come on but no other light. The orange wire on the brake light switch seems to be constant hot.
Pictures show my fuse panel - and also the spliced brake switch white wire.
Also the brown nd orange wires that are coming from my heater were not hooked into anything.
Any ideas on what I should check? I’ve traced wires and don’t see any melted or anything. Thanks!