RE: "file size reduced dramatically for uploading with significant image quality reduction"
The metadata shows your file size as 1.9MB, and pixel dimensions of 16130 x 5206 pixels. That, and the banding in the sky makes me think you might be reducing the file size by increasing the JPG compression?
Starting with a copy of the original, see if you can resize (downsize) the pixel dimensions to something like 1200 or 1600 pixels wide, and I think the file size (in MB) will take care of itself without as much quality loss.
Look at the metadata for the other photos in the Gallery, the file size for most is less than 1MB, and that is because they have reduced the resolution to no more than 1200-1600 pixels wide.