Brake line too close to header tube?

That’s close! You can install a fire sleeve like the do for spark plug wires to close to a header tube. Even though you can’t sleeve it easy, wrap it up and use zip ties farther away from the heat source. Wrap it around or fold it over and gain some peace of mind.
Yep, too close.
It could, can, be that close if it were a over axle tail pipe. Definitely not okay near primary tubes.