When I became I werewolf I killed Belethor and the guy who runs Warmaiden. These were my main points of commerce. Is there anyway I can fix this or am I boned?

You... killed them.

A family member or someone is supposed to replace them. I have yet seen or herd of any replacements. That is not to say they will not. try to wait several days. It may take a week of in-game time to reset with new merchants.

I killed a fresh meat seller on a Contract, he has never been replaced.

I tried to use Spoiler Tag but they dont work here.

When you first became a werewolf, you never had to leave Jorrvaskr. I usually just stand in place or play with those archery targets until the effect wears off.

Killing merchants and quest npcs = bad. If there's a way for someone to replace them, then that's news to me. That's why many people hate having dragons attack cities, killing off merchants and quest npcs.

Another good plan is to go back inside the Underforge and wait it out.