You are still not answering the question. I understand that the doctrine of penal substitution states that God gave Himself in the person of His Son to suffer instead of us the death, punishment and curse due to fallen humanity as the penalty for sin. I held PSA for most of my life, I studied PSA as a graduate student in seminary, I taught PSA. I know you do not mean it this way, but it is a little insulting to assume that I do not even grasp the basics of a theory that I held and taught for over 30 years.
In the near future I may interact with your link. I told you then I thought it was an excellent presentation of PSA, but I do not see a need to go line by line as the reason I do not hold PSA is because I do not hold the philosophy of justice it assumes to be divine justice (I've explained this before). I agree with your passages on the link, I disagree with the assumptions.
Yes, PSA holds that Christ had to suffer instead of us the death, punishment and curse. But that was not my question, was it? I do not think it intentions but you are obscuring the issue rather than answering.
Let me try to explain the question and then I'll rephrase it. Christus Victor, Ransom Theory, Moral Influence Theory, Government Theory, Recapitulation Theory...almost every articulation of Reconciliation holds that Christ had to specifically suffer the Cross at the hands of "wicked men" - NOT under the law at the hands of "godly men" but at the hands of the Romans (who were in power in that area at that time). PSA is the only exception that I can think of that does not hold Christ's death on the Cross an absolute necessity. I'll speak for my view, but it applies to most others as well (not yours). Christ could not suffer and die under the law of God. Christ had to suffer and die under the world's justice because it is this justice, these powers, that Christ came to overcome.
Now to the question - I think that we can both agree that Christ did not die under the law (that would be stoning at the hands of the Jews, not crucifixion at the hands of the Romans). Here we are talking physical death. We both know that PSA requires (as you posted and I affirmed twice in this post). But the curse does not require Christ to suffer the cross. The curse requires Christ to die a physical death. The punishment (the "wrath to come") does not require Christ to suffer the Cross. The "wrath to come" would require Christ to experience an spiritual abandonment at least associated with the "Second Death".
You have not provided an answer as to why Christ had to suffer the Cross. Why not have Christ suffer under God's law (under the Law God gave to the Jews)? It would be a horrible death, and it would be under the law). How do you believe that the Cross itself was necessary?