I have about twelve cavities. most of which are gum line. the gap between the gum and the tooth is quite large. is this typically something that can be fixed, or would it most likely require the tooth/teeth to be pulled?

Yes. : Twelve cavities are alot. Most cervical caries at gum line can be fixed. A tooth colored bonded resin filling will look good, may help to close gaps, and can last for years with a better care and improved diet. However some of your problems might be related to gum disease which if not treated may lead to tooth loss. Ask your dentist.

Treatment: You have both infected teeth and infected gums/bone. Time is not your friend, the sooner you are treated the better the prognosis. From your description you have been putting off professional dental care. Please don't put it off any longer.

See below: Speak to your dentist and have a treatment plan. The general dentist may want you to have a consultation with a periodontist if warranted to have optimum results.