CLR
I've cleaned up a few rusty tubs with CLR cleaner and a green scratch pad, tons of elbow grease. Also, most large grocery stores should have a Rust Remover liquid in the laundry aisle, brown bottle. As tough as it is to get that rust off the tub, I don't think you should worry much about stained clothes, unless they are white and you leave them long time in the washer when it's finished.