From the EXIF, I know what you mean. Anyway, the photo is not bad after editing. Vote to support you. Pls continue to shoot more stars.
Next time, you can use Shutter Priority to set the safe shutter speed (from 1/200 to 1/300, depending on your hand stability). Then, increase the ISO to 400 to capture more background lighting (noise is not obvious in Canon DSLR). The aperture and the external flash (with TTL) will then work for you. This is my actual experience.