do what you think is right. that's all that can be recommended. have you considered talking to your broker about moving your account to another brokerage because you can't get answers (only if its practical and your brokerage may not care if your a/c is relatively small.
if the broker is say showing $20,000 as proceeds and accrued market discount of same amount the reported gain on 8949 would be zero.
you do have the option of reporting exactly as the broker did then using type c transaction and the adj basis to come up with what you say is the correct gain or loss.
