This is not proof, do you understand this? Tsunade does not prove their confidence nor do they state "Yes, Tsunade can heal souls".
You are arguing off of assumptions and character confidence, not actual evidence.
These aren't even direct character statements that state without plausible deniability that Tsunade is capable of healing souls.
This is not the case, Orochimaru is not judging her off her current capabilities. Orochimaru is choosing Tsunade to heal him solely because Tsunade is the greatest hearler in the world.
Orochimaru knows Tsunade personally, he knows she's the best healer in the world, and he knows he can potentially bribe her to help him. Therefore, if Tsunade can't do it then he has no chance, she's his best option not that she can actually do it because Orochimaru proves he doesn't know her full capabilities. Thus, he is not a credible source as he is proven to be not fully knowledgeable.
No? It didn't matter if Tsunade could or couldn't heal Orochimaru. The point of the arc is whether or not Tsunade would help or hurt Konoha, not if she can actually heal Orochimaru.
In fact, Tsunade was never going to heal Orochimaru so it once again did not matter if she could or couldn't.
Your entire argument literally depends on the possibility that Tsunade can actually heal souls.
You do not have undeniable evidence that Tsunade can heal souls.
There does not exists a single feat of Tsunade healing souls.
Therefore, it's at best Possible that Tsunade can heal souls since your entire argument is based on character's beliefs in Tsunade. Which is already shaky evidence since it's entirely character conjecture with no support and we are shown that one of them (Orochimaru) is not fully knowledgeable about Tsunade.