Is it really your position that the Universe is under Satan's control, and has been since his fall?
Seems pretty obvious just from looking around, doesn't it?
Matthew 4:8-9, "Again, the devil taketh him up into an exceeding high mountain, and sheweth him all the kingdoms of the world, and the glory of them; And saith unto him, All these things will I give thee, if thou wilt fall down and worship me."
Would it be possible for Jesus to appear in 'Satan's Creation', formerly that of God?
It's still God's creation.
How would Satan wrest(take) control of Creation from the very hands of God
He didn't.
if he was defeated and cast down into the pit of Hell and imprisoned?
He wasn't. Yet.
Wasn't the purpose of his imprisonmet
He isn't. Yet.
meant to keep Satan from disrupting the Cosmos in the way that the theory you presented suggests?
He did disrupt it, back when he purposed in his heart to usurp The Throne of God.
Wouldn't it have been necessary for Satan to have won the war in heaven to have disrupted the univerese in such a way?
He and his angels were cast out of heaven.
There has been no war in heaven. Yet.
There exists a severe problem with any thory which suggests that Satan is in control,
not in the least; it is the entire problem with everything, everyone, indeed, with all creation. That is why the great Clockmaker will one day fix some clocks, for good.
or that any influence he might exert over God's universe would not be undone by the power of God.
It's happening. It will be. Not in our time. Not in good time. But in God's time.
It would seem that the only inluence that Satan could have is over beings which posess free will to choose Satan's path over God.
As to "beings": Satan can affect us through our relationships, ourselves, God, Our Saviour, our spouse, our family, our church, our friends, our neighborhood, our school, our city, country, world. Get the picture?
1 Chronicles 21:1, "And Satan stood up against Israel, and provoked David to number Israel."
2 Corinthians 2:10-11, "To whom ye forgive any thing, I forgive also: for if I forgave any thing, to whom I forgave it, for your sakes forgave I it in the person of Christ; Lest Satan should get an advantage of us:for we are not ignorant of his devices."
The fact that the materials in question do not posess free will (IE. Energy and Matter) are outside Satans jurisdiction.
Ephesians 2:2, "Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience:"