However, one's understanding of how to apply the moral law and the objective existence of the moral law are two different things.
Perhaps, but if no one knows the objective moral law and the means of determining it are beyond the realm of science then it is practically useless. This is what religion proposes; an unconfirmable deity that exists beyond the realm of human understanding made objective rules that he, and only he, is going to be able to understand or ever know... what good is it then?
And if this is the case, then could one not also say that god is following his own subjective morality as well, and the only reason we should believe it to be objective is because he is more powerful than us? Objective morality therefor is nothing more than "might makes right.".
... it is still possible to establish the existence of real standards supported by the moral law and the corresponding suppositions or expositions of the religion itself.
Do tell how this is done. Religion is full of contradictory moral statements; do not kill one another, kill the Canaanites; do not be an adulterer, rape the unmarried women of a conquered nation; love one another as you love yourself, believe they should spend eternity in unimaginable agony for disagreeing with you.
One must cherry-pick if one is to find any sort of morality from any religious text; Jesus said he did not come to replace the old law, Mohammad said both really good and really terrible things... the closest religion to being "moral" by today's standards would be the likes of Jainism and Buddhism and even they get things wrong.
So again, even if there is an objective morality to be found in religion, it is meaningless because we do not know which bits are and which bits aren't. And the bits we do find moral oddly enough coincide with what we find to be moral as a society.
For example, if I said that it is wrong to torture handicap babies for fun, I would be correct, and I would be correct about that whether it had ever happened before or not.
Why are you correct, though? I completely agree it is terrible thanks to my code of ethics, but there is no objective truth telling me this is wrong. The baby will live, the baby will die; the torturer will live, the torturer will die. The Earth will keep on spinning until it doesn't, the sun will keep on burning until it stops and the universe will exist until it doesn't. There is no cosmic punishment for breaking the objective rules, there is no punishment at all outside of society agreeing that the torturer broke the commonly accepted code of conduct. What is the point then of an objective morality if it is neither knowable nor enforced?