1. Should Osama Bin Laden have been taken alive?
If you believe that the USA should hold itself to the highest possible ethical standards, you may conclude that Osama bin Laden ought to have been taken alive. However, you should be aware that, as well as the case that he was an enemy combatant whom U.S. forces were entitled to kill, there are huge practical difficulties surrounding what should have happened to him next if he had been captured.
As with most yes/no questions about complex issues, the first step is to ask several more questions. The first one is how much additional loss of life you would be willing to accept for Osama bin Laden to have been captured alive. It appears that at least four other people besides bin Laden were killed during Operation Neptune Spear, and there were many women and children throughout the compound. Given that it would be significantly more difficult and dangerous to have captured bin Laden alive, doing so would have placed more lives at risk, including those of United States Navy SEALs.
Another question to consider is what should have happened to Osama bin Laden if he had been taken alive. It is very difficult to see how he could have received, and be seen to have received a fair trial. Any defense lawyer would presumably have argued that the saturation media coverage assuming his guilt would make such a trial impossible. As long as bin Laden were to be held alive in a military prison, he would provide a focus for Islamist terrorism throughout the world. To execute him without trial would have caused a worldwide uproar.
If you believe that the United States should hold itself to the highest possible standards of due process, you may conclude that bin Laden ought to have been taken alive in any case. However, you should be aware that there are very significant practical objections to this, as well as the moral case that he was an enemy combatant.