JK Rowling, I'd assume. It's been noted that 'mal foi' is (kind of) French for 'bad faith', although Rowling says she didn't think of this when she came up with the name.
Draco Malfoys wand: Hawthorn and Unicorn hair, precisely ten inches, reasonably springy.
Draco Malfoy. He does not have a canon middle name but many people believe it is Lucius after his father.
In the book they didn't; Lucius and Narcissa abandoned Voldemort during the battle and ran around shouting Draco's name. They were then sitting alone together in the Great Hall after the battle ended. For the film, four different endings were filmed for the Malfoys. Presumably they chose the one with the Malfoys walking off to show their betrayal of Voldemort, or something like that.
For all the Malfoys have a change of allegience at the end of Deathly Hallows, JK Rowling has never stated whether they give up the Dark Arts altogether. The only things she's said is that Draco's son, Scorpius, would probably be an improvement on Draco.
He ends up marrying hermoine after she leaves Ron due to several horrible sexual experiences.
Yes
Yes
Malfoy's name in Harry Potter is Draco. Then there is his father (Lucius Malfoy) and his mother (Narcissa Malfoy).
If you mean house elves, there are two main ones. The Malfoys pervious house elf's name is Dobby and the Black family house elf's name is Kreacher.
They are on the list of the most rich immaginary people.
Yes, when it becomes dangerous and painful.
Roy G Biv made up the name for colors.