Jehovah's Witnesses and demonology... In the JW viewpoint do demons know that God will destroy them? Are they intelligent and rebellious?

I'm not a JW but I know from their literature that they do, indeed, know how God will deal with those rebellious and intelligent demons. They will quote James 2:19, "the demons believe [there is one God] and shudder." And they quote events in Jesus' life where the demons were subject to His authority both then, and in the future, such as in Luke 8:26-31.

There, the man of Gadara, who who possessed by a legion of demons, fell at Jesus' feet and shouted, "What do you want with me, Jesus, Son of the Most High God? I beg you, don't torture me!" The demon, Legion, "begged him repeatedly not to order them to go into the Abyss." That is a future event, so Jesus permitted that legion of demons to enter into a herd of pigs instead.

Revelation deals with the Abyss, that future confinement for demons, but JWs might interpret that as a state of annihilation. Mainstream Christianity seems to differ, saying they will eternally suffer for their rebellion. But that is another question! See Revelation chapter 9 and 20:3.

Yes, Satan and his demons are well aware of their fate. Notice this account from Luke 4:33 and 34...

Now in the synagogue there was a man with a spirit, an unclean demon, and he shouted with a loud voice: “Ah! What have we to do with you, Jesus the Naz·a·reneʹ? Did you come to destroy us? I know exactly who you are, the Holy One of God.”

Clearly, the demons know that Jesus will destroy them.