All good points. I don't think that anti-war sentiment was significant in our decision to stop at the 38th parallel. It didn't take the (non-existent) protest of the soldiers' parents to convince the civilian control over the military, which knew about all the issues you raise, realize that it was the better part of valor.
Maybe you would agree, or have some clarifications to add to this: I think maybe that the allied mistakes that led to the Korean war happened at Yalta and in our decision not to support the Koumingdong. Stalin hadn't been adequately warned at Yalta before WWII was over as to how the allies would react if he engaged in Soviet imperialism. Chang Kaishek's rout emboldened the communists everywhere. We had appeased the Russians at the Elbe, and we had embarassed them in the Berlin airlift. And North Korea was ripe for the picking due to its wholesale domination by Kim Il Sung's dictatorship.
Prelude to the Korean War: Setting the Stage
yes, I agree with your excellent analysis of the Allied failure at Yalta, and the failure to support the KMT . that's absolutely a big factor when Stalin decided to iniate the Korean War. He took it as a sign of American weakness ??????