For the human head, which direction is anterior, and which direction is ventral?
Humans are are upright in their anatomical position - fig. 1 - from which all directions and terminology stems.  


Figure 1: Anatomical Position

Because of this, anterior is normally the same direction as ventral and posterior normally the same as dorsal - fig. 2.  



Figure 2: Normal directions in humans

Cranial anatomy is a special case, however, as the entire axis of the body bends round during embryonic development as seen in fig. 3.  



Figure 3: Bending of the developmental axis

This leads to the cranium being a little odd, where dorsal is equivalent to superior and ventral to anterior in this area of the body only


Figure 4: Resultant difference in neuroanatomy conventions

However, for convenience, anterior and posterior retain their original directions even in this area.  Therefore you could eliminate a large amount of your difficulties by just using these terms instead for most of the body.  



To answer your specific questions:


  So I conclude that human nose is anterior


Yes


  So I concluded that humans' top head is dorsal. Yet ...We call humans' top head anterior


The top of the head is technically dorsal, however in practice would never really be referred to as such, instead being superior.


  In humans, is humans' chin ventral from the eye too? or posterior?


The human chin is both inferior to the eye (looking straight at the face in the coronal plane) and anterior to the eye (but only marginally).  It's more obvious if we look at the tip of the nose instead, which again is both inferior and anterior to the eye.  


  In humans, is the nose anterior too?


Yes, the nose is anterior.