Hmmmm...a lot of well written questions.
You are correct, translators of the Bible did tend to place the scriptures categorically. I took a class in college that went over these different categories that you are intelligent enough to see on your own. The different categoies should help you to determine your question. Prophecy is not literal as is Poetry. The rest is fairly literal context.
The Old testament is an accounting of earlier days and works hand in hand with the New Testament in interpreting later parts of the Bible. Spiritual maturity helps readers understand the more 'harder to accept' parts of the Bible. We have to account that 'free will' that lead to sin was the reasonings behind what you might consider now to be more 'absolute' [that you call cruel].
Addressing creationism. Consider the 'holes' in the scientific theories that exist. Yet people believe them. Why is that?
I'd ask you to place all the earth's molecules and substance in a huge cosmic bag and shake them up and hit them with a 'big bang' and would an 'earth' be created? Of course not.
We see no 'new' earths being created. We see desolute planets in our solar system, but not life.
We also no see the evolution of creatures, but rather 'distinction' of many creature (including the great apes and monkey that evolutionist say we are akin to). Why aren't these evolving.
Okay so I've pointed out holes in evolutionism, however, one thing that 'even' scientists agree upon is the 'historical' accuracy of the Bible.
We also find prophecy predicted long before man felt it possible to be revealed.
We find a 'book' that is held in its integrity despite years of translations in different languages, etc. Outside of Shakespeare...there is no other 'book' with this history.
It is simple enough to consider man and how we create 'all' that we do upon the earth. Yet, the earth is designed as a sound ecological system that is able to survive beyond that of man's errors.
To assume that there is no creator would be illogical from the standpoint of history. Most cultures have held that there must be a god...despite not agreeing upon the god it is.
The Bible answers these questions. Other religions have failed in accuracy. The Bible has withstood all tests and holds proven accuracy that even scientists can not deny.
The agnostic books I am not completely familiar with, but they could be the Apocrypha (uncannonized writings found during the same era the Bible was). Some believe the Apocrypha is Hebrew or early Messianic Jewish writings. Most faiths do not include these as regular scriptures (I've not heard the term agnositc for these though). I'd have to research further.
Wonderful questions and as stated earlier they are written with much intelligence. Thanks for posting these.