weird turn signal issue

The odd thing is that the signal flasher should NOT be getting power with the key shut off. Are you sure the 4x flasher switch was not engaged?

Otherwise, this shounds like you have some wires crossed up somewhere.

My strategy is to divide the problem into sections. Take the wiring diagram, and I can help you in you need, and for example, disconnect the signal switch.

This now separates the

flasher going to the signal switch

brake light switch power going to the signal switch

unhooks the front left/ right lamps and wiring.

unhooks the rear left/ right lamps and wiring

Now you can access EVERYTHING that comes and goes right at the switch. You should be able to take the wiring diagram and ID brake light switch power coming in, which is hot with/ without the key on

So tromp on the brake pedal, and you should be able to identify that, and confirm the switch is working

Now probe the wire from the flasher. Pull the flasher out to confirm.

Next, ID the wire colors for

left rear

right rear

right front

left front.

You should now be able to take a probe and hook it to a 12V source with an inline fuse and probe those connections, and prove that each lamp is working. Additionally, when you inject power to the front lamps, the dash, hood, and fender indicators, if equipped should light.

This is a simple step by step process. Eliminate as much as you can, then deal with what's left over.