Should I read the bible when alone?

You can read and understand the bible in solo reading, but it was written for different cultures at different times and in different languages. Taking the context into account creates a very different story to prima facie reading in English. You miss a lot of the depth when you don't read with tradition in mind, and some miss the point entirely. You should read the bible alone, but you should also read it with the Church of the Ages, with the many living and dead who also read it.

Why did God seemingly kill King David's child as punishment for David's adultery and murdering

The very centre of our religion is why God punished the innocent, Jesus, for the guilty, us. 

God in the Old Testament would periodically punish children along with their parents and wives with their husbands. But have a bigger picture, God permits the death of countless babies in history. Evil is not only done to evil people. Not just evil people die. We all die.

In the specific case of God causing King David's child to die, God used the fact of a child's death to punish its parent and force that parent to repentance, especially of the murder he committed when he heard the child's mother was pregnant with his child. God's own child would one day also be killed in order to gain King David grace from that repentance.

God kills everyone and God will kill you. Death is a certainty, life is a gift.

The basis of strong success in Western Civilisation is in having faithful, married parents and a stable family life.

The basis of strong success in Western Civilisation is in having faithful, married parents and a stable family life. Western values, from which we get our success, are those values we inherit from Christianity and Christiandom.

Watch a Mr Calvin Robinson being interviewed by a Mr Carl Benjamin, of an online news organisation called The Lotus Eaters, on this topic, and let us know your own views in the comments.
https://youtu.be/tpuUFtQs6dg

A prayer for enemies

Curse my enemies with righteousness. Let them do what is right whether they intend to or not, let them live good lives, whether they land in heaven or hell. Lord, fill them with repentance and righteousness. Force their hand to do what is right, in the light and when unseen. Let good come where they intend ill.