Aftermarket stereo wiring

When I bout my car it came with a DVD player. I took it out to replace the lights on my obc (I bought the bulbs for it from autozone $5 for two. I tried to solder them on but couldn't get it thin enough so I just put the metal pieces back in the plastic and shoved the new bulb in and it was a nice tight fit and still works). The wiring was a total mess!!! Anyway.. I have a few questions.
The main power wire doesn't have a fuse on it like the manual says it should. I had a dead battery and had jump started my car multiple times and now my screen flickers. Is it because it was missing the fuse and jumpin the car messed it up? And should I install a fuse?
Next I have the prerun wires for the 6 disk changer and wanted to put one in but my stereo has nowhere to plug it in. Do I have to splice the wires, buy some kind of adapter? Or should I just give up? Lol.
And lastly I have random wires that aren't connected can you tell me what they are?
These two are the same wore just different angle.
This is the same colore as another wire deep in the dash that isn't connected to anything