Savant, sorry to tell you but that is not a TGB Key West. In the photos of the ID/SN plates you posted (good thinking), look at the one that says Guangzhou Panyu Huanan Motors. Huanan made that bike. It is a mainland Chinese manufacturer, not Taiwanese. Sells a lot of bikes in China, but to compete in the international market, it is notorious for making bikes that look like popular bikes and even giving them the same name. You know the popular Sachs Madass? They make a Huanan Sachs (not with the word Madass in the name).
Maybe you can get parts, repair it. Me, I wouldn't even try. You could put it back or Day 1 Original Condition and it would be junk.