Good posts...
There is no doubt that Germay's fate was sealed, and nothing could have prevented "The Fatherlands" eventual defeat, the Question is at what point was defeat inevitable?
To paraphrase from Kennerly's "The Rise and Fall of the Great Powers", The greater combanation of economic power will (and has) always defeat(ed) the lesser.
Based on that premise, Germany might have been able to defeat the Soviet Union, and/or Great Britian. When Hitler declared war on the US (to honor the terms of thr tripartie pact) after Pearl Harbor, The fate of Germany was cast in stone. With the Combined resourses available from all of occupied Europe, Germany's production of armaments (and availability of Troops as well) was dwarfed by the US/UK/USSRs capability.
The ME-262 was the most advanced aircraft of the war indisputably, but would not have effected the final outcome. The Red Army would have still been raising the Soviet flag over the Reichstag in May 1945. There was no way the Whermact could have stopped the Red Army after the German 5th Army was encircled and destroyed at Stalingrad.