Turn signals not working, blowing fuse

Bear in mind that disconnecting the bulkhead may have FALSELY removed the "problem" because if you were on the wrong track, and disconnected the bulkhead, it may have broken a circuit that "normally" would have shown that particular reading.

Remember: Ohm's law. It is difficult to measure low ohms readings. That is why I try to go as far as I can with voltage readings.
I=E/R. This means as an example, that a circuit showing 1 ohm only draws 12.6A or whatever battery voltage is. Not only that, but bulbs become much lower in resistance when unpowered/ cold filaments. I have no idea, offhand, "let's say" what the parking/ tail lamp/ marker circuit might read for continuity when unpowered. It will not be very much. Ditto for headlights

Another example. Reverse light circuit, a pair of 1156 lamps. They are rated at 27w, so 2x is 54 watts. P=IE so 54= I x 12.6. That's about 4A

R= Esquared/ P so R + 12.6 squaared / 54 is about 3 ohms. Again that is operating conditions so that reading will be less when the bulbs are unpowered. You can measure a few bulbs to get an idea. 1157 stop/ tail lamps are same wattage on the turn/ stop filament, 54 watts