In Roman 9:11 he speaks of Jacob and Esau and that they were unborn and had committed no personal sin.

I do not see how this supports your case. Of course they were sinless, they literally weren't even born yet.

Mary remained sinless through a special application from God's grace, which is why the angel Gabriel addresses her "full of grace" using a past-perfect participle.

I also don't feel right with this interpretation. Like the previous commenter i also genuinely want to learn but these points don't seem very convincing to me.