I agree according to John 3:18 we are judged according to whether or not we believe in Christ. Double predestination teaches that we cannot believe unless God has chosen us. So that would ultimately make God responsible for the unbelief of nonbelievers since they are incapable of believing unless they are chosen which would make God unjust for judging and condemning people who are incapable of believing. This is just one example amongst many of why predestination does not work.
There seems to be two issues here:
1. Just what of the fall (related to Adam) is passed onto the rest of humanity?
2. What is the difference between wrath earned and righteousness imputed?
Adam and the fall:
What came about as a result of Adam's transgression was the severance of fellowship from God for the rest of humanity. This is what some have coined as "sin nature". The propensity to sin is a different issue than choice to commit sin.
Propensity to sin means that the heart is naturally inclined to that end. Now will the person manifest sin in external action is a matter of conscious choice. I'm suffering from greed in my heart but do I make the choice to rob the bank? One is the manifestation of the state of the other. The dismal state of the fallen heart is what's inherited from Adam. One poster said: We do not start as a clean slate. This is true.
The wages of sin:
Punishment for sin committed is something the sinner earns. That punishment is ratcheted upon the severity of the sin committed.
If one high school student gets into a fist fight with another high school student because they both have egos bigger than the state of Texas and think they need to prove themselves; that's one type of sin. Yet if another student who thinks he needs to prove some point, goes into the school and guns down a bunch of students and staff; that is a different (and far more serious) manifestation of sin.
If never redeemed; all three students will face punishment for what they did. The one who massacred a bunch of people will face a far more serious punishment at the judgement throne than the two who fought each other.
This is the case for all who commit sin and all commit sin based on the natural inclination of the heart that is dead in trespass and sin. Some commit more heinous sin than others. And the choice to do so is a function of human conscious.
The doctrine of election:
Now the doctrine of election states that because the human heart is deceitful above all things and desperately wicked; this requires the intervention of God to regenerate an individual unto salvation. God does this because without His intervention, no one would believe. This is because of "total depravity".
Now "total depravity" does not mean "depraved totally". The conscience is still intact. Humanity inherently knows the difference between right and wrong. We are capable of making moral and ethical decisions. That is a different issue though than faith (or trust) in God. We do not bear that naturally. That requires a supernatural awakening.
The wages of sin earned is predicated upon what is done. That is not "double predestination" because the sin that is committed is what earns the punishment. It's also not imputing Adam's personal sins to any individual who did not commit them. The flip side of this though is that if any of us were put in Adam's position, we would have done the same thing. The fall was inevitable because of the temporal nature of the created.
Now one may argue that it is "not fair" that God awakens some unto salvation and leaves others to bear the consequence of their sin. Yet if God were to do what was fair; all would suffer the wrath of God for their sin.