I see you have thought this through very carefully, and probably done quite a bit of research. Because you have a long history of hemoptysis (coughing up blood) it might be a good idea to start with lower-concentration saline. Higher saline doses are a powerful irritant which promotes coughing and some people here say can lead to bleeding if you are prone to it. If the lower saline works, then maybe increase - based on consultation with the ID doc.
Has the bronchoscopy and lung wash been suggested by pulmonology?
Sue