Was Adam created first, or were both Adam and Eve created at the same time? (Genesis 1 vs Genesis 2)
Adam was created first. This is the only way that the chapters can be interpreted to coincide.
Why did YHWH place a Tree of Knowledge of Good and Evil in the center of Eden? What was its purpose, if not to tempt the humans?
The Tree's purpose was to give man the choice as to whether or not he wanted to follow the will of God, which continues to this day.
If Jesis was Gods only son, who was Jesis' mum? And what stopped them having children? Or did they just have daughters?
Jesus wasn't created via procreation. Since he is part of the Godhead, he has always existed (John 1:1-5).
Are things good because god says them or does he say them because he's good?
Morality is inseparable from God's character. This is not a tautological argument, that God=good, but rather that God is characterized by his goodness. We as humans are able to come to many of our own concepts of morality thanks to reasoning and intuition, God in his omniscience understands it better. In other words, we need no outside definition of "good".
To the OP,
Why do we need God?
If God is real, good, and omniscient and he says that we need him, then it would follow that he is correct. The issue is whether or not you believe that God is real, good, and omniscient.
What is God's real name?
God refers to himself by many names.