If you really want to know what Islam is then you will have to shun thoughts such as Islam spread by the sword / Why did the Prophet (pbuh) had so many wives etc and etc. The answers to such criticism has been given on numerous occasions.
Also there are no mistakes in the Quran (you mention that the prophet (PBUH) should have corrected the mistakes). The All-Knowing and All-Wise Allah cannot make mistakes. The only problem is that some people may interpret verses in a way that meets their agenda but this does not mean the correct interpretation by the learned scholars is not available. In fact interpretations by the companions of the Prophet are also available.
It cannot be emphasized much that Islam is not support killing of any human (for any life) unjustly. Killing a person (innocent) is like killing all of humanity and saving the live of a human is like saving all of humanity.
I pray that you will study the facts and may Allah guide you in seeking the truth.
