My single stage metallic has become dull

I have no doubt that you're right. There are details I overlooked when I bought it that I noticed later on, such as masking lines on the antenna, overspray on several components in the engine compartment, and sloppy masking lines on the trim. So the previous owner didn't bother to remove anything at all for paint. Just masked and sprayed. But it's not his problem anymore...
But you're havin fun with it, right? That's what it's all about.