Several things have bought me to think of that , the missing ninth God of the ancient time as was called Shor .
Is it possible so that he become several famouse dragonborns of history like Wulfhart, Thalos and finally the Dragonborn.
Explaining also why the seatof Sovngarde is vacant .

Wulfharth, Talos and Tiber Septim are all explicitly Shezzarine, which are avatars of Shor. You are correct.

The LDB is also often believed to be Shezzarine, though that's a weasely thing to say.

Ldb?

The Last Dragonborn.

We reenacted his life by fighting and defeating Alduin yet again in the spirit realm when he came to cause trouble. Personally, I think what we saw was just Alduin's aspect, or ghost. He's too small (I know gameplay, but still) and he never acted as if he wanted to eat the world. The fact that he wasn't absorbed? He just went back to his original self and Alduin returned to sleep until it's truly time for him to wake. Alduin seems to wake up every now and then too early, and Shor puts his butt back in place. And he just did it again.

Though, if it were just his ghost or avatar, it seems odd that it'd need a whole prophecy for it, when Shor did it before. Who knows.

But anyway, yea, I'd say we're Shor. Him telling his people in Sovngarde to not fight's like him saying "Stay back! I got this." Although, it'd be better without the heroes interfering. Oh well.

I've been plugging this idea for a long time, but I've also been plugging the one that Alduin has basically un-mantled himself by trying to step outside his role of World-Eater and trying to become World-Ruler, which is the domain of a different aspect of his. He's basically caught in the lurch between godhoods, reducing him to "just" a powerful and unique dragon. Or so I believe based on a reverse-engineering of the way mantling works.

Continuing the off-topic theme, I've settled the lameness of Alduin in Skyrim by the fact that Alduin was still weak. After eating half of the souls in Tamriel his hunger would have and thus becoming the actual World Eater, Thartaag/Satakal. In other words, according to my headcanon Alduin was originally a regular dragon that mantled the world-eating aspect of the Time Dragon due to his ever-growing hunger for souls.