How do you, as a believer in the God of Abraham, justify God's behavior?

I love how people spout off about not being able to "understand" god, yet go on and on and on about how god is merciful yet vengeful and can do what he wants.
Either you don't understand him and shouldn't be talking FOR him, or you are pretending to be god and think you can speak for him.
Contradictions abound! Not surprising.

I would never attempt to "justify" God's behavior. He is holy and He is sovereign, and He can do anything He wants--including taking me out of this world in the span of a heartbeat.

I don't believe God does any of these terrible things. He isn't there to keep us from experiencing pain, he's there to help us through it. God doesn't cause people to sin.  Oh good!  Maybe you can explain how the fire and brimstone that god rained down on Sodom and Gomorrah "helped them"?  And the how pain felt by the pregnant mothers who died at the end of the Israelite swords (along with their unborn and innocent babies) was eased by the knowlege that their death was "god's will"?  And what sin David's newborn son committed that could possibly have been so much worse than his father's murder of Bathsheba's husband and his adultery with her that the infant had to die?  I have more questions when you have answered these!

God pretty much sums up that we are not able to completely understand Him because His ways are higher than ours (Isaiah 55:8-9).

You are comparing God to human mentality and God is so far above us & our way of thinking. He created life. He created us. He knows everything. He knows the heart of every single person ever born. He knows the impact of their choices in life, and the impact of their death (present and future). He knows every thought ever thought.

God is all light and no darkness. He is holy and just. I think people question these things when they do not see God as completely holy.  God is not capable of evil. If you do not believe He is capable of evil then all that is done must be for a divine purpose even though we may not understand it completely. Someday we will. 

Most importantly, I can't justify to myself worshiping an invisible, unproven deity that would perform such heinous acts towards those that he claims to love & created.  

If you do not believe in God to be Holy your view of the Bible is skewed
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yea, I don't think so. I think my view is crystal clear.

Let's see . . . God is omniscient, omnipotent, omnipresent, and omnibenevolent.  He created humans, with full knowledge that he, the perfect being, has created something extremely flawed, plants a tree that he forbids them to touch, knowing that Eve will be tempted by the snake that God created, and knowing that he will have to punish Adam and Eve for crimes that he knew they would commit.  He had to know.  He's omniscient.  Then, after a few generations of incest, murder (often commanded by God, even though he has made commandments against it), and other bad behavior, he decides to flood the earth to cleanse it of his disobedient creations (even killing pregnant women (and their fetuses), children, and all the animals that weren't lucky enough to have been chosen by Noah to board the little boat. 

e,His people had warnings to act right or else
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why create an imperfect being, then demand they "act right" because their behavior pisses him off?
Sounds like a toddler having a tantrum.

And in this book, this inerrant word of his, he gives instructions on how to purchase other people, when and how to beat them, when to marry the women you rape, how much money to spend while purchasing a wife, what sort of bloody sacrifices are appropriate, adds a little pornographic material, demonstrates his might with stories of slaughter, asks his favorites to kill their own children  as proof of their fidelity and love of him, gives directions on when to kill entire cities of people, when to rape, when to pillage, etc.

It's an amazing book, that justifies God's actions by simply being the book that people believe was written or inspired by God himself.

God doesn't need justification. He is God. If He created this world, He can destroy it. If He created us, He can destroy us. But the God I know is merciful and loving unlike other so called gods.