With moderately severe cryofibrinogenemia that requires treatment, what type of specialist is the best to consult for this disease? is it considered to be a form of vasculitis?

Usually: Usually a dermatologist would treat this because you do get a vasculitis that affects the skin. An immunologist and rheumatologist may treat this also.

It depends: Cryofibrinogenemia can be primary, or secondary to another illness. If it's primary, it's a blood disorder and increases your chance of lymphoma, so you should see a hematologist/oncologist at some point. It can also be due to a rheumatologic illness (eg lupus, rhuematoid arthritis) and either way, it has symptoms like vasculitis, so a rheumtologist should also be on your team.