As I understand it, according to islamic history, God sent his messenger, the Angel Jibril (Gabriel in latin) to Mohommid to teach him about love, peaceful relations, compassion, mercy, kindness, charity etc. This message is recorded in the Koran. So God's messenger is the Angel Jibril and the receiver of God's message is Mohommid.
So if angel Jibril taught of gentleness, and the persons writing the Koran write of a command to act with barbarity and cruelty, then is a lot of the Koran NOT the teachings of the angel and therefore we can assume/assert NOT of God?
I don't really understand where you're getting the first assumption, that the entire message was supposed to be about happy things, from. And then the rest mostly just builds from that point. It sounds somewhat like the argument you're trying to make is that Gabriel always said nice things in the earlier texts, and that's not true. In the Jewish texts, his only mention is in the book of Daniel, and he tries to explain to Daniel some visions Daniel had seen, but it still doesn't make a lot of sense. In the Christian texts, his only canonical appearance is in the first chapter of Luke.
Mohommid though was not a literate man, but wished for the angel's messages to be recorded in writing. So in fact, it was not Mohommid who wrote the Quoran, nor angel Gabriel, but others, one of whom was a woman...
I don't see the significance of one of them being a woman, unless you're saying that women are unreliable.