I would like to have a source about that.

I understand the mantling process but I can't find a source that states that Talos(Tiber,Wulfharth usw.) has manteled Lorkhan.

I don't know if he mantled him more than was him already and took his original spot.

Load up Skyrim,

Notice any Shor-shrines?

QED

Obscure sources aside, hes replacing the dead Missing God (Lorkhan/Shezzar/Shor) and assuming their place among the other deities. His shrines in Skyrim depicts serpent (a creature usually attributed with Lorkhan, much like Dragons are to Akatosh) appearing from his own mantle, and him shoving a sword down its gullet.

If Talos took Lorkhan/Shor's place why isnt he in the Hall of Valor?

Its the realm of the dead. Talos is still very much alive, unlike his mirror-brothers. Shor isn't there either...well, in a sense.

If he's Lorkhan now should he take over his dominions as well. Sovngarde is his realm (1 of them in any case) and It would make sense that he could manifest there without a problem.

But there's also...
The heroes spoke as if they've talked with Shor who told them his pretense there would harm them.

Identity relations work in a very funny way in The Elder Scrolls.

Sovngarde is shor's realm, shor is of lorkhan but he is not Lorkhan. Shor is a broken piece of lorkhan like Shezzar/Akatosh and the Shezzarines. The whole mantling process of Talos was more of three broken parts or Lorkhan (Shezzarines) combining into one.