God let's men choose hell for the same reason God let Adam choose rebellion. He is not a dictator. He gave man free will and will let man exercise it.
As for suffering, that was never part of the plan. Adam chose rebellion in exercise of free will and suffering is a consequence of that. Could God stop it? Yes...but that would amount to being unfair to evil which like it or not has a legal right to be on earth because man, i.e. Adam, who God gave dominion over the earth let it.
However, what God has done is send Jesus to redeem man from the consequences of said rebellion. This would be completely manifested during Christ's second coming when this world passes away and there would be a new earth whereby there would be no suffering or tears or sickness or death forever. Just as Job's latter end was so blessed he forgot all his sufferings, just as Joseph was able to call his son Manasseh because he forgot all his earlier afflictions, such will be the new world, all it's inhabitants would by virtue of its peace and fullness, forget their suffering.
We see suffering and death and sickness and pain as real tangible consequences of Adam's rebellion. In the same way we will see the tangible restoration of Christ's obedience on the cross in the fullness of time.
And again, feel free to regard all this as total nonsense but it is the Christian worldview and it does have an internal logical consistency to it 🙂