INST Fuse blowing

You have power both sides of fuse? That fuse should be hot both sides at all times.

"It's possible" you damaged the dimmer control

Depending on your meter, measuring the oranges to ground might show what you think is a short because the lamp bulb filaments are such low resistance.

This in part is why I suggested the tail lamp lashup above. It draws enough current that if you hook power to one end and the dash lamps (one of the orange wires) to the other, it will LIGHT those lamps while itself is glowing "at some brightness". But if one is actually a dead short, all that lamp will do is light up full brightness.

In other words you need a test lamp that draws enough current to "sort of" operate the load you are testing. The fact that you are using a 12V test lamp means that if you hook it to a short, all it will do is to "light up."

You could even use a headlamp for this, which draws more yet.

Probably an even better way of looking for this now that you have separated part of the orange.........is to connect a test lamp to power on one terminal of the lamp, and with the INST fuse pulled, hook the other terminal to the orange side of the fuse clip. This will of course feed power to the orange side and you can go from there.