Interesting discussion. My thoughts on angels and the Devil Below. Please note I approach these thoughts from a JW or Christian perspective.
Do spirit creatures have emotions? Well, emotion is a chemical and biological response from a physical body. But, the bible says we make the spirit creatures happy?
The bible says the angels found women sexually enticing and wanted to try physical sex. They experienced lust and passion. However they are not male and female. They are sexless. Did any of the angels want to try homosexual sex too?
The above thinking illustrates a fatal flaw in the logical understanding of the bible writers. The angels were sexless and had no biological bodies, yet they had the same exact emotions and flaws that humans had. Does this make sense?
There is one reason why the devil wouldn't exist. How could he have made a choice to do bad things if he is like god and not subject to human emotions? If he does have "human emotions", then that means god creates him that way. God made those base human emotions that got the devil and humans into trouble.
Second. If god can do and know everything, then the devil does not make sense. Why? Here are a couple questions. Does god know everything? Does god know he is right, or is there a chance god is wrong? If god can't be wrong and he knows he is right, and if he can do anything and I mean anything... Then when satan fell and sinned, since god knows he is right, he could have wiped satan out and removed his ever having existed from the spirit creatures minds. If god knows he is right and he can't make a mistake then there is no purpose in allowing millions of his angelic children and billions of his human children to suffer and die. He could have used the power he had to simply say, well Satan can't be right. Letting him create an issue out of this will result in billions of deaths for no reason. I'll just either fix Satans faulty programming or I'll wipe him out. Then I'll make all living things forget Satan. It's the same exact end result. I know I'm right, in fact it's impossible for me to be wrong, so no need to let billions die.