The quick answer to most of your questions is an issue of sovereignty. God is sovereign. An illustration is in the book of Job 1:6-12. Here we see that Satan (the leader and most powerful fallen angel) came before God and was only able to influence Job's life after gaining permission from God and God limited the power Satan was given.
1. Where did the man's will and the demon's will start and end?
The beginning and ending of the demon's will rests within the sovereignty of God, what He gives them the power to do and not to do at any given moment. The quantifying of man's will leads to the debate over man's free will vs. God's sovereignty. We can discuss that further if you would like as that is a topic with a large scope.
2. How did the possessed man recognize jesus? If the demon's told him that jesus was real and identified him, isn't that an unfair advantage? Why can't demons tell all of us which god is real?
How the man recognized Jesus is beyond the scope of my knowledge but it is quite possible that the demons did tell the man who Jesus is though that is not revealed in the text. The middle of your question is again answered by God's sovereignty, they cannot resist His will. Demons certainly could tells us who God is. James 2:19 says "Thou believest that there is one God, thou doest well: the devils also believe, and tremble." However, they are in rebellion against God so they would certainly have no interest in testifying upon His behalf.
3. If the man's free will is strong enough to drag the demons within him toward jesus, why couldn't he have excised them himself?
Here again it isn't the man's free will that allowed him to drag the demons toward Jesus but rather God's sovereignty limited the power the demons had over the man. The man was helpless against them until he met Jesus.
4. Why would the demons relinquish control since they obviously knew that meeting jesus wouldn't go well for them?
Again God's sovereignty.
5. Why would a loving god allow demon possession?
One of the toughest questions. Why would a loving God allow...? There are a lot of different reasons why things happen. Some explained, some not. I will defer to a similar question the disciples asked Jesus in John 9:1-3. And as Jesus passed by, he saw a man which was blind from his birth. And his disciples asked him saying, Master, who did sin, this man, or his parents, that he was born blind? Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him." The last part is the focus: that the works of God should be made manifest in him. The casting out of this demon was a testimony of the works of God and a testimony of who Jesus is. If you notice the story ends with the man wanting to follow Jesus and his disciples but Jesus refused him and told him to return to his town and tell everyone he meets what God has done for him and this testified upon the Christ's behalf.
6. What happened to the demons ultimately? From the story, it appeared as though they died. Can demon's simply die and no longer exist?
The parallel passage in Matthew 8 sheds light onto this in verse 29: "And, behold, they (demons) cried out, saying, What have we to do with thee, Jesus, thou Son of God? art thou come hither to torment us before the time? This "before the time" has to do with the final judgment. Demons and unbelievers will share the same fate: "Then shall he say also unto them on the left hand, Depart from me, ye cursed into everlasting fire prepared for the devil and his angels." (Matthew 25:41) They did not die, nor will they die. They will be tormented in everlasting fire.
7. Why did the demons drive the pigs into the sea to drown?
I've also wondered this as well as why the townspeople would beg Jesus to leave. The text doesn't provide an answer to either of those questions at least to my knowledge.
1. Where did the man's will and the demon's will start and end?
The beginning and ending of the demon's will rests within the sovereignty of God, what He gives them the power to do and not to do at any given moment. The quantifying of man's will leads to the debate over man's free will vs. God's sovereignty. We can discuss that further if you would like as that is a topic with a large scope.
2. How did the possessed man recognize jesus? If the demon's told him that jesus was real and identified him, isn't that an unfair advantage? Why can't demons tell all of us which god is real?
How the man recognized Jesus is beyond the scope of my knowledge but it is quite possible that the demons did tell the man who Jesus is though that is not revealed in the text. The middle of your question is again answered by God's sovereignty, they cannot resist His will. Demons certainly could tells us who God is. James 2:19 says "Thou believest that there is one God, thou doest well: the devils also believe, and tremble." However, they are in rebellion against God so they would certainly have no interest in testifying upon His behalf.
3. If the man's free will is strong enough to drag the demons within him toward jesus, why couldn't he have excised them himself?
Here again it isn't the man's free will that allowed him to drag the demons toward Jesus but rather God's sovereignty limited the power the demons had over the man. The man was helpless against them until he met Jesus.
4. Why would the demons relinquish control since they obviously knew that meeting jesus wouldn't go well for them?
Again God's sovereignty.
5. Why would a loving god allow demon possession?
One of the toughest questions. Why would a loving God allow...? There are a lot of different reasons why things happen. Some explained, some not. I will defer to a similar question the disciples asked Jesus in John 9:1-3. And as Jesus passed by, he saw a man which was blind from his birth. And his disciples asked him saying, Master, who did sin, this man, or his parents, that he was born blind? Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him." The last part is the focus: that the works of God should be made manifest in him. The casting out of this demon was a testimony of the works of God and a testimony of who Jesus is. If you notice the story ends with the man wanting to follow Jesus and his disciples but Jesus refused him and told him to return to his town and tell everyone he meets what God has done for him and this testified upon the Christ's behalf.
6. What happened to the demons ultimately? From the story, it appeared as though they died. Can demon's simply die and no longer exist?
The parallel passage in Matthew 8 sheds light onto this in verse 29: "And, behold, they (demons) cried out, saying, What have we to do with thee, Jesus, thou Son of God? art thou come hither to torment us before the time? This "before the time" has to do with the final judgment. Demons and unbelievers will share the same fate: "Then shall he say also unto them on the left hand, Depart from me, ye cursed into everlasting fire prepared for the devil and his angels." (Matthew 25:41) They did not die, nor will they die. They will be tormented in everlasting fire.
7. Why did the demons drive the pigs into the sea to drown?
I've also wondered this as well as why the townspeople would beg Jesus to leave. The text doesn't provide an answer to either of those questions at least to my knowledge.
