Barbarians they might be, and maybe impetuous. But stupid they aren't. Blow up a nuke now and a large part of the world would be against them.
No, their strategy is to dhimmi-ify Europe, and radicalize Pakistan and Indonesia. India will be surrounded by Islam or China, South America will be threatened by Chavez and the communists. China will block Australia. Africa is always an non-player in global politics, except as a jumping off point to reconquer Spain and Europe.
When the time is right, and there is no one who can or will come to our defense, the bombs (if or when they have bombs) will go off. The point about the bombs in the US won't be to win the war, or even start the war, but to declare the war over, to present us with a severe setback when we are prevented from any response by lack of allies, and pressure from our non-allies to not respond.
You can see the effort and effect now in the ballyhoo about Tancredo's commonsense announcement about nuclear retaliation. If a nuke goes off, and the politics do not allow retaliation, the USA will be seen as totally impotent by the rest of the world.
They certainly would not waste their time on 'minor' things like airplanes crashing into buildings if they had nukes.
That depends on how long-term their strategy is. You punch the leader in the nose to get his attention, and remove the image of impregnability. Having shaken faith in the leader (USA), it's easier to separate the lesser followers away from the group (Spain).
What they must build, before they can use the nukes, is the idea that they are totally untouchable yet they can touch us whenever they want. This can be because we can't find them, or because local and global politics won't let us make the appropriate response (see Tancredo nuke flap, see Tancredo immigration flaps). Then, they need to use only a few to get the world to bend to them. Had they started with nukes, the USA might have been able to get a pass on nuking them back, or a pass on a massive sweep of tanks from Morocco to Pakistan.
This is roughly the same strategy as used by the Old Man of the Mountain and his assassins. It was very successful, up until the Mongols came through and killed everybody in their path.
Your entire post makes a lot of sense, but it presumes too much. For one thing, it assumes our President and other leaders will be cowards, willing to see their nation going up in smoke without striking back due to foreign 'pressure'. It also presumes that these barbarians are patient to the extreme, and have a long term strategy to conquer the world. While I believe they'd love to conquer the earth, I already see the world fighting back against them; even in Pakistan, Iraq and Afghanistan, where we see Muslims killing off thousands of their more extreme brethren.
The Philippines are not tolerating their muslim extremists, nor is Thailand or China. They fight back with crushing blows. From all appearances, it even seems the Islamofacists in Iran are beginning to lose power to the people, (who remember better days). Turkey is a secular government that won't tolerate a theocracy and Africa is.... well, as you said, just Africa.
I don't believe for a moment that people like Osama bin Laden and al Zarqawi would 'sit on' nuclear bombs until they felt they had already won the war and then use them as an "announcement" that it was over. These people are cold-blooded killers, and while not stupid they are quite insane, their minds swallowed up by their sick religion and their hearts turned to stone by their hatred. THEY WILL LOSE, and Christ The King will reign.