Wow, that looks bad
Apart from going down the legal route for a retube, I can only suggest that you try several applications of Shmuffex. Although it is primarily a mould remover, we have had some success on rust marks. Some of the pics seem to show streaks where rusty water has run down the tube (These should be removable). The problem is if hot metal particles have landed on the tube and melted their way into the fabric, you might find that even if you clean them, they come back later.
I hope you get a resolution.
Regards
Steve