Your points are quite valid, but the funny thing is while Dr. Paul may have a few faults, the other candidates certainly have much, much more.
But if you think about it, Dr. Paul's faults are not really faults, rather, they are practicalities. Libertarianism, Conservativism, Liberalism, and other ideologies have many different related ideas, some practical, some not.
So let's go through each of your issues one by one...
Dr. Paul supports cutting the income tax but not the corporate tax or the excise tax. In the ideal libertarian world we could cut all taxes and let the states take care of anything, unfortunately the US has amassed 65 trillion dollars in debt and we will still need some taxes to pay off the debt. However, we could certainly get a major headstart by reducing the biggest one, the income tax, to 0, and replacing it with nothing.
A non-interventionist is by no means a pacifist. Dr. Paul supports the army, supports having a strong national defense. The Constitution calls for it, and it is definitely necessary. What he doesn't support is unnecessarily intervening in other countries' affairs.
As a result of this policy, if we were to withdraw all our troops, we could save 1 trillion each year, while the income tax only accounts for 800 billion of the government's profit. So yes, it is quite possible to terminate the income tax, but only if we change our idea about our foreign policy ought to be.
The pork barrel issue is an interesting one, and this once again goes into the practicality of Dr. Paul's libertarian views. If Dr. Paul was a perfect libertarian, he would absolutely not propose any pork legislation. However, as a Congressman Dr. Paul takes the interests of the people first, and his own views second. If the federal government is being robbed by corporations and special interests daily, while the ordinary people you represent receive none of the taxes they pay, if you were in Dr. Paul's position, would you let the corporations and special interests continue to steal money from your constituents, or would you fight and try to at least win some of the money back for them?
It's a dilemma for any libertarian. In a perfect libertarian world, there would be no taxes, therefore there would be no need for pork. Unfortunately, in our welfare big-government society, it is both impossible and impractical to be a complete libertarian, with our system as messed up as it is. Dr. Paul is strongly against pork, but he also recognizes that unless you completely change the system around, playing the system is the only way to get the money back to the people. So while his actions are contrast to a small section of his beliefs, they coincide well with the larger, overall theme of Libertarianism - that is, returning the power and the money to the people, even if some early sacrifices have to be made, simply because the system is the way it is.
Finally, about the enthusiasm about Dr. Paul's supporters. Dr. Paul does not promise us a perfect world, 100% not. Maybe some supporters think that, but surely not anyone level-headed enough to really consider his policies. However, compare and contrast his views with the rest of the rat pack in the presidential race. Is there ANYONE who understands economics, reality, and foreign policy as well as Dr. Paul? And is there ANYONE who believes in the Constitution as much as Dr. Paul does?
I disagree with Dr. Paul on many issues. All of us do. But Dr. Paul isn't running to become the dictator of the United States. He's running to become the President. And being a president, you have to follow the Constitution. In the end, all of Dr. Paul's views go back to the Constitution, and that is what makes him special, and what binds us together.
Dr. Paul is not perfect, but he's our best hope for freedom. So stop being a naysayer, and realize that not all positions are perfect, and not every person is perfect (in fact, nobody is.)