Well, everything is working as it should!
It took a long time, but I was finally able to gather all the correct pieces, and I now have a functioning AUX port on my 2003 Focus. Sweet!
I ended up using the FRDW-AUX that I showed in the picture, along with this
harness. I have a lot of extra cable, but that's okay.
For now everything is just sitting in my glove box. I haven't had time to actually mount anything yet. But, it works, and for now, that's all I need.
Thanks again jay-rod05! Without your video I wouldn't have believed that this was possible.