Ignoring questions looks fun, let me try:
If we were capable of achieving what God demands of us, then did we need Christ for salvation?
Is Christ not necessary, or is man helpless? When man is helpless, does God lower His Standard? or remain steadfast and Glorify Himself? Did He take away the law for us, or did He achieve something for us that we could not?
Why is Christ the only way?
Ok, great question. Again, the Law was implemented for 1500yrs+-, therefore we trust that this was not a superfluous exercise on God's part merely to toy with our faculties, making us believe that we could achieve something that intrinsically, we could not. God demanded obedience, and condemned man accordingly for their failure to do so. Therefore, we do not charge God with both a frivolous institution of a Law, and a sadistic penalty upon transgression of the Law. Thus, the both Law and its enactment was righteous. And, its purpose was to reveal the hearts of man, not the ontology or inherent capacity of man, ...which, again, by implication, it delineates or potential capability to do what's right, as the Law would not have been implemented otherwise.
So now, since it is our corporeal bodies (flesh) that arouses and entices us to sin, and due to lack of wisdom of the vices and hedonism of the flesh, we succumb to its allurements, we recognize that it is by our own volition that we violates God's Will. Therefore, man needs a saviour, ...but only for those who are willing to recognize and acknowledge this (this is the volitional part again).
Therefore, Christ did not die for all, as in universalism. For, if we were incapable of choosing the good, then mutually we would be incapable of choosing Christ, and since Christ is God's plan for all, then all would be saved. But, in actuality, man is free to choose good, and free to chose Christ, for all are not saved.
Romans 7:13-25
7:13. Therefore did that which is good become a cause of death for me? May it never be! Rather it was sin, in order that it might be shown to be sin by effecting my death through that which is good, so that through the commandment sin would become utterly sinful. 14. For we know that the Law is spiritual, but I am of flesh, sold into bondage to sin. 15. For what I am doing, I do not understand; for I am not practicing what I would like to do, but I am doing the very thing I hate. 16. But if I do the very thing I do not want to do, I agree with the Law, confessing that the Law is good. 17. So now, no longer am I the one doing it, but sin which dwells in me. 18. For I know that nothing good dwells in me, that is, in my flesh; for the willing is present in me, but the doing of the good is not. 19. For the good that I want, I do not do, but I practice the very evil that I do not want. 20. But if I am doing the very thing I do not want, I am no longer the one doing it, but sin which dwells in me. 21. I find then the principle that evil is present in me, the one who wants to do good. 22. For I joyfully concur with the law of God in the inner man, 23. but I see a different law in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin which is in my members. 24. Wretched man that I am! Who will set me free from the body of this death? 25. Thanks be to God through Jesus Christ our Lord! So then, on the one hand I myself with my mind am serving the law of God, but on the other, with my flesh the law of sin.