Well, the most immediate think he was fighting was the "tyranny of the majority", the idea that a body of which he was a member could by majority vote, agree to take rights from one who voted with the minority. Sound farmiliar?
I'll attempt to answer your three excellent questions as they pertain to me: 1) Is John Galt a man I would follow?
Qualified "Yes". He fights with the only weapon he has access to which can hurt those who are unjustifiably hurting him. Does he have a right to do this? Do you have a right to shoot someone burglarizing your home and endangering you or your family? Now I agree that Galt and the gulchers get a little hypertheoretical about this and ignore the value of charity, freely given when needed. I had a conversation with Billthedrill about this.
2) Is the world better off that John Galt lived?
Yes, definitely. Yes, people died. So what? Americans and British died in the Revolutionary war. If you had the power to alter history, would we still be paying King George tax on tea with no seats in Parliament? Would Hitler still be gassing Juden and homos? The point is that people in general were better off with the FINAL results of Galt's decisions than they would have been had he gone along to get along. People allow their children to undergo painful operations or medical treatment because they judge that the long term results will be superior enough to make it worth the sacrifice.
3) From where did the genius of John Galt come?
I have to agree with you on this one, from God. Rand misses this, as she is doomed to do by her atheism. But take ancient Israel as an example. There was no law against becoming rich. Employees, slaves (more like what we would think of as indentured servants), and animals were all to be treated with kindness and respect. Provision was made for widows, orphans, and the legitimate poor to support themselves by their own labor (prohibition on gleaning right to the edge of a field), thus preserving their dignity. But there was nothing that said that a farmer who was smarter or harder working than his neighbor was a bad guy.
I can't see holding yourself up in the Highlands of the Rockies, while the rest of the country goes down the shitter, as a particularly noble thing to do. Where would we be today if Washington and the boys just headed west to open up new territory and declare a new country instead of fighting it out east of the Appalachians. And in the process the 66% of the country ambivalent or opposed to the war being left to the tender mercies of the Red Coats. They didn't because they understood sacrifice for a cause greater than themselves
On your answer for question #2 I think there is a qualitative difference between soldiers dying in battle fighting for freedom and people getting crushed in a war of attrition by the productive elite against the looters. I see this as if I burned down my shop with some of my employees inside because I have the tax looters trapped inside also. I admit an imperfect analogy but you get my point. There are innocent people in Rand's world that are just trying to make a living. She pretty much rolls over them on her way to Nirvana.
My final point is that question #1 was a personal preference sort of thing. I would, personally, have trouble following John Galt. I get the feeling he would sacrifice all his troops to the last man to destroy his enemies. Sorry, but my guts and his glory, as they say, makes for a bad leader.