BTW, in re the Congress's power to declare war, many people argue, and I would agree, that the framers did realize that there would uses of force short of declared war. Among other examples: they were in the midst of Indian operations where nothing was ever declared, and one of them, under General St. Clair in the Northwest, was a disaster -- which led in 1792 to the first Congressional inquiry into Presidential use of force. All of the founders were in office then, distributed in both branches, and there was lots of party feeling and venom, but nobody brought up the idea that not having officially declared this operation made it illegal.
But I think all founders (even Hamilton) were also clear, and said on many occasions, and for very deep reasons, that they did not want the president to have the sole power to start wars. That that power was to be, as Madison put it, a "joint possession." This was a key difference between a president and a king.
The upshot for me is that Congress's power to declare war was not meant to be a legalism, but a basis for authority. It has the power to declare a war rightful or unrightful. Nobody can stop them, and that power is vested in the constitution. If the president ignores them, then they can cut off funds; that is their power of compulsion. (If the president makes an end-around their fund cutoff, then they can impeach him. But of course that action, and all preceding, are ultimately constrained by the support of the people for either side.)
On this view, the fact that most uses of force have been authorized by Congressional acts that didn't use that word declaration isn't an erosion of power or a loophole. It is rather a recognition that has been there since the beginning there is a continuum of uses of state force to defend or advance state interests, and while the executive usually takes the lead, the more controversial the case, the more of Congress's authority is needed to make the war rightful.
Now the question of ending wars is completely unaddressed by the constitution. You might say the Congress has the sole power of starting wars, so they should get it. And you might say the President has the sole power of conducting wars, so he should get it.
But in fact, neither has either power sole. The president has always, since Washington's time, been able to initiate use of force. And the Congress controls the funding, which clearly gives them substantial control over conduct.
So AFAICS, they both have a joint possession of the power of ending it.
Michael