1. War should be used in self-defense, when self-defense is necessary. Should it always be a LAST resort? That depends on what you consider a last resort. A last resort to preserve a country's very survival? Or just to preserve its well-being? Or just to preserve its right not even to be threatened? Or just to protect against a potential threat? Or just to protect financial interests? There are varying levels of "being threatened". Some, financial interests for example, probably don't necessitate war. Some, defending the very survival of a country for example, probably do. Some in the middle, I don't know. I don't know where the line is drawn.

2. I've never fought a war myself, so my opinion can't matter that much. But I have family who has done so, and we have what we see in the media, and what we can read in books; poor sources though those may be, that's all we have. The President has even more than that; he has the opinion of the most qualified people in the world, namely generals, who presumably HAVE fought wars, and know war inside-out.

Our legislators aren't murderers; can they pass laws regarding murder? Our judges aren't all pregnant females; can they interpret laws about abortion? Our President isn't an immigrant; can he enofrce laws about immigration? The answer is yes; you don't need personal experience to understand something. I don't see any reason a President who never personally served in the military would be more willing to go to war.

3. In self-defense.