There's not a single elder scroll... These artifacts surface every now and then. A large collection of them is secured into the imperial library guarded by the Moth priests. Who knows how many of them are still in the wild waiting to be discovered or rediscovered?
Now that you mention it, what happened to the Elder Scrolls when White Gold Tower was sacked by the Thalmor? Surely they could recognize one or two?
As for the topic:
No, I can't agree. Alduin's Wall can only be seen by a dragonborn, seeing that you need to spill your blood to even open the gate, not to mention you need Akaviri translation notes in order to read it.
And he couldn't know about Alduin's return. Nobody else in Skyrim possess the knowledge of the prophecy, even the history maniac Esbern didn't now the full details
So, sorry OP, but your take on making Ulfric look bad has failed