Does God allow us to fall, I say yes, for the purpose of understanding. The knowledge of evil (sin) came through the law, but the knowledge of good (righteousness) came through Christ. We have eaten from the tree of the knowledge of good and evil, for the tree contains both the understanding of evil (the understanding of sin and the understanding of law) and the understanding of good (the understanding of righteousness, which comes through Christ, not the law). We had to eat in order for us to understand the Father and who He is; that He is love; that He is righteous.
When we make the mistake of thinking that righteousness comes through the obedience of the law in order to avoid punishment, our own mind conceives the thought that if we are avoiding discipline, we are being righteous. This is what I believe to be the mistake of the Pharisees. They avoided punishment through the sacrificial law. But that law has now been done away with. So now, does our righteousness come through the obedience of the rest of the law? no, it comes through the understanding of Christ and who He was and what He did while He was here.
Righteousness (doing what is right) came through the example of Christ and the life He lived, acts of kindness, acts of gentleness, acts of forgiveness, acts of compassion, all contained and done through love for mankind. Righteousness comes through acts of love towards others, not through acts of obedience of the law.
Of course, this is my understanding.