But furthermore, I want to Will to be the observer. In this way, I think we come to a unique understanding of Transcendental Idealism. If the Will is the observer, then this boils down to mundane objects being dependent on the existence (i.e. idealism) of the Will, but independent of his experience (transcendent). After he makes them, they don't depends on his watching them every second in order to exist as the Rambam already said in the Guide. They are not a part of His existence though they depend on his existence.
(1) I forgot to mention: the one kind of ding an sich is hidden from pure reason. That is to say there is human reason which is flawed because of our being prone to reason baldly. But there is human reason that is pure. But even that reason (which is called by Kant) pure reason has a limit. Then there is the reason of the Will which created reason in the first place. That Will will have to have a higher type of reason.
And so one kind of ding an sich is hidden from pure perception and another kind is hidden from pure reason. That is the Creator of pure reason is hidden from pure reason.
(2) I am not claiming to have any knowledge of Kant or Schopenhauer. I wish I would have to the time for that. Here I am only making two suggestions based on my merge understanding of some of their major points. At some point I tried to get into Kant but it takes a tremendous amount of time.
(3) The basic questions on what I wrote up above are these: the third man problem concerning reason. and the fact that observation and experience in the above context are the same.
The that means to say I am saying there is a difference between pure reason and the reason of the First Cause. [This is well known from the Rambam.] But then we would have to have a higher reason beyond that to make the reason of the First Cause into Reason. I tried to answer this question in the above essay by the idea that God created reason itself so we don't need to postulate anything beyond that.
The second question is that Transcendental Idealism postulates the existence of the object is independent of experience [beyond experience] but dependent on the existence of the observer. If we say First Cause is the observer it seems hard to say things are beyond his experience. But for monotheism I think we have to say that.