Patrick, that is one of the reasons I gave up on using black paper years ago. Very hard to get a soft or faint look.
It is very hard to get shadings right.
I ended up going back to white art paper and lead pencils, then invert in PhotoShop.
Shading is an art form in itself but can be achieved fairly quickly.But you may prefer to work with black paper.
Everyone is different and will eventually discover 'their own way'
I can't see any problem in your sketches above, but I can't compare to the actual image you saw. Only you saw it and know how the sketch should look.
They look good to me
