We literally couldn't be more similar . I went through the same steps. First time doing anything like this and felt like a miracle when it worked.I'm not a smart man when it comes to electronics, I got it to work using the relay and only chopping off a little bit of the wiring, and I called it a win
But doing it "right" couldn't be any simpler. It's actually the unnecessary harness that makes things confusing.
The instructions are literally:
1. Attach the lights' red wires to the aux wire
2. Attach the lights' black wires to the battery
That's it. I highly recommend it (no pressure lol). Here is an image of my functioning setup: