Is this black mold/wall damage fixable without professional help?
That section of the wall must be cut out.   The drywall and plaster and then behind it must be cleaned.  You would cut out about 12&quot; over the molded area.   I see mold too next to it.
Fans help having a huge mold issue.   If you have a flood and standing water fans are not the fix though.   They just keep the issue from getting out of control.