Thanks for testing. The image appears as all black when you load it into Slicer because the same SOP instance UID was used in all the files. DICOM export is very complicated, there are many rules to follow, so if you need to create images from scratch then I would recommend to inspect the content of DICOM files coming from clinical scanners and use the freely available DICOM standard to understand each field and why it is there.
The PETDICOM extension throws errors because it misses some of the fields required for computing SUV: