I took the page from Military Budget WikiPedia topic. That page is not under challenge which implies to me that there is a concensus about the data included. The data may not please people but I imagine that it has undergone much scrutiny.
Some of the spending that created the total debt is the spending on the Military when revenues would not cover it. Like today. Not all but some. I would expect that the "debt" portion of the chart is the portion of the current interest attributed to spending on military when the debt was incurred. IMO, all Congressional mandated spending is "legitimate" unless it is ruled "illegitimate" by the appropriate judicial body. I may not like it, but that does not make it illegitimate.
general welfare involves something directly affecting everyone, not a localized area. Roads are included becasue of commerce -- they have to go everywhere to make everything available for everyone. The mail can be under that catagory. But disaster relief and food stamps are not. (And if you compare the rebuilding after Camilla and the rebuilding after Katrina, the old way was much more efficient.) Daniel Boone wrote about a meeting with one of his constinuates after the Congress took the first step in disaster relief due to a fire and an excess of funds. He admitted they made a big mistake. But you really have to study, and not simply have an opinion based on pie in the sky whims.