Only to make the point that Man's proper morality is inherent to his nature, regardless of his origin, and also to make the corollary point that a loving God would not command Man to follow a morality that was in conflict with his God given nature.
I totally agree with this, and I think that's the tradition Islamic stance on morality, nature, and God's command.
A loving God would respect his creation by allowing Man to make mistakes and discover morality for himself
Clearly he does, because we do. If didn't allow it, we wouldn't be able to do that. In fact the Quran commands this, and forbids blind acceptance, instructing us over and over to reflect. Although it's posed as a question, "Do you not reflect?"
Nor would he interfere with, thereby destroying, Man's purpose for living, which is the pleasure and happiness he derives from using his God given faculties to overcome evil in his instinctive drive toward safety, survival and prosperity.
I'm not sure I accept this as a purpose for living, but a function of nature which preserves life. If God exists, and he interferes, it can only be to return man to his purpose for living. Further, If God exists, and created man, the purpose of living in His to define not ours. Although we are free, as you said, to reject that purpose, and create our own.
I don't accept the word "evil" to describe man's instinctive drive stuff. Original sin is a uniqly Christian concept (as far as I know). Muslims believe in something called "naffs" the lower soul, which is not evil, it just desires the pleasure and happiness of this world, which is good, in fact neccassary for the preservation of life, which is one purpose. But they also believe in the "Ruh" the higher soul, whose purpose is to seek and know God.