On the no UK & France DOW over Poland bit, the POD would probably have to be Hitler not annexing Bohemia in March 1939. Leaving it nominally independent even though with a client regime would have left Appeasement as still viable while rearming went on. IF Poland still grabbed Teschen (sic) defending it would have been less popular than iOTL. While letting the Nazis and Siviets fight it out would have its attractions. Implausible though I agree.The problem with a 1939 war between Germany and the USSR is that France and Britain will jump in the war over Poland, so that's a no go. Staying neutral in that is impossible for them politically. Really the only viable "one on one", which really means Germany+vassals, just no British or US belligerency, is after Germany has conquered Europe in 1940 and Britain is knocked out of the war via diplomacy (Churchill would have to be dead for that to be an option, which probably means the torpedoing of the Nelson in 1939 works and he dies as the ship sinks) after the Fall of France. Post-peace Britain is not going to be rejoining the war due to the Axis pact and the Quit India movement meaning a renewed British war would happen without India. And Britain would lack LL to sustain a war effort if they quit in 1940. After peace Germany has access to France's $3 Billion in gold reserves stashed all around the world, same with Belgium and the Netherlands, plus their colonial resources. Trade with the US is still going to happen in that case because the US cannot afford to totally relinquish the European trade market, which Germany would dominate post-war. Britain would not be able to make up for the shortfall and the approved military spending in 1940-41 wasn't enough to make up for it either. No LL also means no major stimulus for US industry that tided them over IOTL until the US entered the war. So they need Europe and Germany would be able to buy. Thanks to American companies making US designs in Europe (Opel) Germany could buy up a bunch of Ford trucks from the US in preparation for Barbarossa and have all the common spare parts already being made in Germany (plus be able to buy more from the US), which would make a huge difference in the East, as they'd have a lot of four wheel drive trucks. Even things like being able to buy or loot oil from the DEI would be hugely helpful, as they wouldn't need to invest in synthetic oil production or synthetic rubber. And they could buy up US made agricultural equipment to free up manpower from farming.
I'm not so sure that any plausible Peace Treaty in June-July 1940 would give Nazi Germany free access to all the FX and gold reserves of western Europe. Let alone enough to buy everything it needs from the US or British Empire to improve its logistics on the scale you envisage. Still, it would be worth finding (or devising if I could) an economic model to simulate the possiblities open to Germany with a rational strategy for organizing European production.