It is probably not a good idea to ask someone to expound a position they do not accept and do not feel they even fully understand.

As with many metaphysical and religious questions, Kant thinks they lie beyond our power to answer them. If you can't stand the frustration involved in accepting this, and insist on finding some more stable position which affords you peace of mind and intellectual self-complacency, then you will find Kant's position "problematic" in the sense that you can't bring yourself to accept it. You may try to kid yourself into accepting either some naturalistic deflationary answer to the problem or some dishonest supernaturalist answer.

It is both theoretically mistaken and morally wrong to regard others as objects of investigation rather than partners in free rational communication.

If being "iron headed" is to be lacking such feelings, then Kant's position is that an ironheaded person could not be a moral agent because such a person would not be rational.

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.

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

It is actually a nice question how far Descartes himself endorses the monological and metaphysically dualistic theory of mind associated with his name and his legacy in early modern philosophy. But Fichte does reject this tradition, by suggesting that an immaterial thinking substance is an incoherent notion, and a rational being whose rationality was not developed through communication with others is a transcendental impossibility.