Would revision rasping of my nasal bone make me worse off? Is it a risk? (Photo)

A very small hump can be rasped off in order to remove the  bony hump.  When the hump is composed of cartilage, this must be cut with a knife or scissors.  When a large hump is removed, osteotomies of the nasal bones are required. For many examples, please see link below 

Rhinoplasty is an excellent and really only way to permanently reduce a dorsal hump. This is often preformed with rasping the bone and cartilage combined with osteotomies.  Best of luck.

I think you have reasonable goals and the rasping down of the dorsum should be done in a controlled fashion, which means that the prominent areas will be taken down in gradual amounts until the preferred shape is seen.  You also have a hanging columella, which I would advise you to improve as well. While any type of nose revision you undergo will have risks of making your nose look worse, there is no way to make it better without doing a revision.  I would advise you to be evaluated by a board certified plastic surgeon, who has experience in rhinoplasty and revision rhinoplasty and will give you a comprehensive assessment of your nose and options to improve it.