When you view something as bright as the Moon, a couple things happen:
--the pupil of your eye constricts. If your eye is sensitive to light, it constricts a lot. This has the effect of making the secondary shadow portion of the star image
a much larger portion of the light going into your pupil. It can make your eye see the center of the field as only partially illuminated, as if in shadow, while the outer portion of the field
still appears quite bright. This normally occurs at low powers with the eye at the exit pupil, but can be seen at other powers as well.
--some eyepieces which are otherwise good performers on deep sky display serious internal reflections. One classic example is Vixen's SLV eyepieces, which are, essentially, not recommended for Moon viewing
because the outer field reflection is severe.
--some designs of eyepieces suffer from a characteristic known as EOFB, or edge of field brightening, which is not an illusion (there is even a post here on CN where someone photographed it). Plössls
do not suffer from this characteristic, so that is not the case here. (the NPL is a Plössl).
When you backed away from the eyepiece, you were seeing a smaller and smaller portion of the field of the eyepiece. You got to a distance where the shadow of the secondary became a huge portion of the image and that is, in a nutshell, what you were seeing in the first illustration above.
As for the second illustration, there are multiple possibilities, but the most likely is simply floaters in your eye. You don't see them normally, but when the exit pupil behind the eyepiece shrinks to the size of a laser beam (and it is very tiny in that scope with really short focal length eyepieces), little bits of flotsam and jetsam in the eye (technically, small agglomerations of protein in the vitreous humor) become visible.
This problem grows worse as you get older. Many older observers don't use eyepieces with exit pupils below 1mm for that reason (1mm exit pupil is where the eyepiece focal length equals the f/ratio of the scope). You see them when looking at very small details on planets or moon when the eyepiece used yields an exit pupil that is very small.
They often appear as dots, as you drew, and sometimes amoeba shapes or bacillus shapes and, if really close to the retina, dark spots. They would not rotate with the eyepiece. If they did rotate with the eyepiece, then they'd simply be dust motes on the bottom lens of the eyepiece.
This scope is f/9.4, so such short eyepieces have very small exit pupils. And, the secondary is large and yields a shadow which is a large % of the field of the scope. And, because you are using an external diagonal, the f/ratio and focal length of the scope are longer than the parent f/9.4 (maybe as high as f/11), this makes the exit pupils yielded by the eyepieces even smaller. So I'm fairly certain the spots issue is merely making the floaters in your eye more visible. Want to see them in the daytime? Open your eyelids as wide as you can and stare at the daytime sky. Without moving your head, move your eyes back and forth. You will see the floaters move back and forth as subtle shadows moving back and forth. They kind of resemble eyelashes in your vision, which is why I said to open your eyes as much as possible to get the eyelashes out of the field of vision.
Since you don't actually view through the telescope with your eye in the position where you saw these things, they are not really of concern.
Sorry about the floaters. Once you see them, you will always see them, especially in Moon or bright planet viewing. But they can be ignored. I have lots of them, but I'm unaware of them 99.9% of the time.