Without getting into Founder quotes, historical points of views, etc., this is how I define "General Welfare; it may or may not be how the Founders defined it per other people's POV but what can I say, it's MY POV....
A "General Welfare" is something that benefits us all and we all pay for it equally, it does not matter if it's Bill Gates or an inner city welfare Mom, we all benefit from fighting diseases for example with the Center for Disease Control, it's in our best interest not to have an epidemic of yellow fever break out, another example might be something nice like Federal Parks if we ALL can enjoy them and pay to upkeep them equally, I don't think people would want to see the mighty Redwoods go the way of the DoDo bird so it's in society's interest to preserve or set aside some things for future generations.
"General Welfare" is NOT things that benefit only a segment of society or only a segment of society pays for such as entitlements, foreign aid, farm subsidies and other things that we ALL don't contribute to or benefit from , just an opinion.
??? Your second paragraph contradicts your first. Everyone benefits from entitlements, since anyone, when down on their luck, will have that safety net. They also improve the domestic tranquility, since there might be open insurrection during bad times. Foreign aid benefits everyone in theory, since it provides us with additional national security, as most foreign aid is in fact military. Farm subsidies keep a continuous food supply at low prices, and even help our export markets.
Not that it matters if the fact doesn't match the theory, if congress decides that something is in the interest of the general welfare, and it doesn't violate any other section of the constitution, case closed. It's foolish to think that somehow the courts are a solution for a precedent that's been with us since our founding. If you don't like something congress or the executive branch does, vote em out. Don't pretend that something is illegal, that is clearly not, because you don't like it. Hell, I think I could make a valid argument that Bush's tax cuts were clearly contrary to the general welfare, but I know that I had no Constitutional grounds to stop it. I'd be laughed out of court after the first filing.