When God created the world. He also created the angels. Among these angles there were archangels. These archangels were more powerful than the other angels. While in heaven before the earth was made, they lived with God and talked to him. However; then God decided to make man. Which he made in his own image. After completing his task, he told the angels to love mankind more than they love him. But there was one angel, Lucifer, who could not bring himself to follow this command. As a result he was cast down into the abyss. The abyss is hell. The being who runs hell is not as powerful as God. Considering that he was cast out of heaven by Michael, another archangel leader of God's army, who does not even compare to the vast power that God commands the Devil would not be able to stop God from pulling people out from hell.
In revelation it also alludes to the end of time. It mentions a second death. This means that there is another death that we as humans have to undertake. When we die we go to heaven or hell, but this may not in fact be our final resting place. We know that God's ideal kingdom is a palace on his creation that is made of pure gold. But is this what we go to when we die the first time? Maybe, maybe not. But the first death is God's way of seeing if we deserve to live in his kingdom with his or not. And if we do not meet the criteria that he has we are condemned to hell. But God will give us another chance. If we somehow prove after the first death that the sinner have paid for their sins, God is able to bring them to his paradise.
This second death exists after eternity. Which seems like a long time to wait in either heaven or hell for the second death. But if the same rules apply there than in the world right now, then when good things happen life seems to go faster. And I assume that suffering turns into something that just flows through the day. (Of course you still remember all that happened to you). Another theory is that when we die time becomes fluid to us. Like is is to God. This way we can easily flow through time. What is eternity to people who are not bound by time?
Yes, if God could, he would save everyone, because God is a loving God. God does not want anyone to suffer in hell. We are all God's children and created in His image. He is a loving God, and most humans cannot fathom how much God loves us. God would save every person if that were His plan.
If God could, He would pull a person out of Hell and bring them to heaven. There's a simple story of a man who had killed 99 people in his lifetime. He went to a priest to seek forgiveness but the priest, after hearing the horrid story of the man murdering 99 people, could not advise the man anything that could save him. For that, the man murdered the priest. He heard of another place that he could seek forgiveness from and died halfway on his path to getting there. The angels came down to inspect the now dead man and wondered if he would ever get to heaven. Surely after killing 100 people the man had no place in heaven. God called to the angels and asked of the man; the angels remarked on the man's life. God then asked to measure the distance from him starting to the end of the path to the next place he was seeking forgiveness. The man had reached a foot more than half of the distance; because of this, God forgave the man's sins and took him to heaven. From this story alone, God can take someone that, from our eyes, had been vanished to Hell and brought him up to Heaven instead.
Because God loves us so much he gave us free will. If we are forced to love God then it's not real love. God has never and will never condemn anyone to Hell we put ourselves in Hell by seperating or cutting off our love and communion for and with him. Because God wants us to freely choose and love him on our own will he would leave us in Hell to respect our wish to be separated from him. If God pulls man out of hell the entire idea of free will is void.