They couldn’t help me and suggested I come here. I have spent 3 days on the Photoshop forum.
I opened it and again, 72 pixels per inch. He reported back that it was 300 pixels per inch but that the Kilobyte size was wrong. So, I created a dummy DDS texture and set it at 300 pixels per inch and emailed it to a friend. I also discovered that when opening any DDS file in Photoshop, even those of other people’s work, was reported by “Image size” as being 72 pixels per inch. Furthermore, taking the 1024 x 512 pixel images as an example, instead of them being 256kb as they are supposed to be they come in at an odd 341kb. However, on opening any of these files on my desktop using my copy of Photoshop, I discovered when using “Image> Image Size” that all of my DDS files are reported to be 72 pixels per inch. To ensure uniformity I set all of my images to 96 pixels per inch and I saved them as DXT1 (No Alpha) to my desktop ready for uploading.
I am doing some modding for Fallout 4 whereby I have used the Nvidia DDS plugin in Photoshop CC 2017 to save images as.