I would like to first mention that I am not writing this comment in order to discount your thoughts in anyway. While appreciating your take on the matter, it might be worth your time to consider different perspectives on the matter.
Everything changes as we look back on history. Cultures, ideas, values, acceptable or tolerable right&wrong... you name it. Perspectives and understanding also changes throughout history. With all these changes continuously taking place, what is the foundation in which we base our belief of something to be either right or wrong? or perhaps something to be correct or incorrect? What you may feel is right would seem wrong to someone else.
The sad truth of it all is that the society claims everything to be relative.
When we consider everything to be relative and not absolute, who gives you or anyone the right to claim something to be correct or incorrect?
Taking on an example of a famous story of a boy who stole bread because he was dying of starvation, would you accept or approve that certain countries still practice dismemberment as the law for stealing?
You see, you need to separate the basis of law (weighing measure of right & wrong) from your personal feelings of the situation.
You specify how God of the Bible killed many including children and explain as to claim its incorrectness based on your own perspective of the matter or rather your feelings toward the circumstance.
Old Testament's context you must understand prior to looking at these stories is that God of the Bible have created a Covenant with Israel through the Mosaic Law (or Law of the Moses) which was an exclusive relationship between the nation of Israel with God of the Bible apart from the other nations. Mosaic Law was based on several factors including 10 commandments, sacrificial festivals, and etc. So if you do in fact separate your feelings from the literal context of a situation, it becomes more clear.

Now, Christians actually believe a different fundamental which is opposite of non-believers and that is Absolute Truth or, in other words, Right & Wrong. Christians believe that the fundamental correctness does not change even though mankind's perspective and understandings of it change over time. An example of this would be, if in someone tried to physically assault you and in self-defense, you attacked the person back and broke his arm; are you justified to say you were right in doing so? Well, Christians believe otherwise. Christians see the matter in two-fold; the act of violence itself is wrong in its nature regardless of circumstance but the intricate feelings behind the person's action can be understood. In this same manner, we are able to stand firm in absolute right & wrong.
Now the most important aspect of Christianity is that the New Testament renounces the Mosaic Law and in its place stands Jesus Christ who became the atoning sacrifice to ultimately pay all penalties for every Sin and wrong doing of all Mankind who choose to believe in Him. The death on the cross literally represents death of the "righteous" for the "unrighteous". For instance, let's say you killed someone and you were caught. The Judge sees you to be guilty and according to a "Just" system, there must be a respective penalty for your wrong doing which equals death. If God then said, okay okay.. I forgive you just go live your life; that would be contradiction to justice. So rather, God sends his Son to die for sins of mankind in order that we may have our penalty paid in full and have life.
In the end... since Jesus is also God (Trinity), it God who came to die in our place to pay the penalty. Thus Christians talk of God's love toward us and his grace benefiting us all.

Ultimately, my suggestion is for you to ask God if he is real. I'm sure if you really want to find out whether He is real or not and if you're skeptical of such ideas and stories shared in the Bible, He'll want to show you the truth.
Christianity is not exclusive to certain individuals who conduct certain actions or claim to know/practice certain Biblical ideals. It is for any and everyone who wishes to find out what the truth is.
I would know.. because for over 30 years of my life, I have hated Christians and its values before I confronted God about my thoughts and questions. Well, we know how it ended up anyhow as I am sitting here writing this post.

Cheers