I think if there were to be a solution to the problem of free will, it would have to be a compatibilist one. Unfortunately, from that it does not follow that there is such a solution. Many philosophers find this an unwelcome message, and as often happens in philosophy, they punish the messenger by ascribing to him an entirely imaginary but untenable position.

Some empirical feelings, such as sympathy, are indispensable parts of certain moral virtues.

Kant is not saying - about freedom or any other subject - anything of the form: "Not-p but we must assume that p." That's close to self-contradictory, like Moore's paradox: "p, but I don't believe that p".

It is often difficult to know about one's own era which philosophers in it will be remembered as the most important ones, but I think it is already clear that John Rawls is the greatest moral philosopher of the twentieth century.

Kant takes a free will to be a being or substance with the power to cause a state of the world (or a whole series of such states) spontaneously or from itself.

There is no author or legislator of the moral law. It is simply valid in itself in the nature or essence of things. We become autonomous only when we obey it, because then our will aligns itself with the objectively valid law, and our choice follows the same law as that we give ourselves. We can think of rational faculty (or the idea - the pure rational concept, not exhibitable in experience) as the legislator or author of the law because reason recognizes an objective standard, and to that extent is already aligned with objective moral truth.

The Russian revolution did not occur until a generation after Marx's death. He was not involved with it, or with what came after it. His works do not describe post-capitalist society, and a fortiori they do not recommend any part of what the Soviet Union did.