From the beginning, there has been a tension in the reception of the Kantian idea of autonomy. If you emphasize the 'nomos' (the law), then you get one picture: the objectivity of ethics. If you emphasize the 'autos' - the self - you get the idea that we make the law. Kant never hesitated in his choice between the two emphases. He emphasizes the nomos (the universal and objective validity of the law).

Kant regards the universalizability test for maxims as focused on a very special sort of situation: one where the agent is tempted to make an exception to a recognized duty out of self-preference. The universalizability test is supposed help the agent to see, in a particular case of moral judgment, that self-preference is not a satisfactory reason for exempting yourself from a duty you recognize. Kant thinks, as a matter of human nature, that this situation arises often enough and that we need a canon of judgment to guard against it.

Kant was a rational theologian. He did not pretend to be a biblical or revealed theologian.

It would be nice, wouldn't it? if we could get comfortable about the problem of freedom. Kant thinks that we can't.

My own view is that Kant's conception of the duality of the good (morality and happiness, the good of our person and the good of our state or condition) is a distinctively modern view.

Kant does represents a distinctively modern view of the human condition in contrast to that of ancient high culture, found in ancient Greek ethics and also in ancient Chinese ethics.

We can make mistakes about what we ought to do, and these are not the same as making bad decisions about what to do.