AFAIK its considered a regular paid ticket. Unless they confirmed at the time of cancelling that there would be no (change/cancellation) fee, then there will likely be.
A) & B) Tweet United and also use Uniteds call back line and HUCA (or in this case HUHTCYA-Hang Up, Have Them Call You Again). Try and get a sympathetic supervisor to help out with extensions/change fees due to US travel advisories at the time.
C) Crapital One paid for the ticket so I dont see them offering any reimbursement on their end.