1) The council doesn't have to re-offer the discount at all, we just happen to know that they do if you make representations within 14 days. There is no legal right to have the discount extended, and they don't have to tell you that they will extend it.
2) The road markings are irrelevant, they don't need any road markings at all. The upright signs on their own would be quite enough, so I'm really not sure why you're so focused on the road markings?
3) At the tribunal they won't have any additional footage of your car, but they will have library photos showing the upright signs.