Don't forget the issue of strategic surprise, mobilization, proximity to German supply hubs/bases, equipment issues, and so much more.
Quite a bit of which are also not really applicable IATL. The strategic surprise is vastly lessened, if not eliminated, the Germans are not as proximate to their supply hubs/bases, the Soviet equipment issues are made much better by being closer to their supply stations and thus having better access to ammo, spare parts, and fuel, and so much more.
Soviet rail logistics in East Poland, mainly impacting the forces opposite AG-Center, were one of the least important issues and bit the Germans so much more throughout the campaign. They did after all have to supply across it while fighting through it. Then the Soviets still were getting wrecked much deeper in their territory, deep into pre-1939 Soviet territory, while the Germans were supplying through Soviet East Poland and into the USSR proper despite having to change the rail gauge on top of the quality of the roads and rail.
By the time the Germans had cleared the Polish rail gap, the Soviet force they were facing were hastily mobilized reservists of much weaker combat value then those they had destroyed along the frontier, yet still gave them significantly more trouble, inflicting greater losses and holding the Germans up for far longer then their counterparts along the border had, owing both to their better supply situation and the worse German one.
Can you post some numbers that show they increased their motor vehicle park through foreign models by 420%?
Standard estimate on the number of motor vehicles for June 1941 is around 650,000 trucks for the Barbarossa forces alone. At the time of the Battle of France it was 140,000. It wasn't ALL foreign models, as German annual production was some 100,000 trucks (although about a quarter of these went into the civilian economy rather then the military), but first, that obviously isn't remotely enough to make up all the difference or even a majority of the difference and, secondly, since the Germans don't have a time machine to steal from themselves in the future, they won't have the vehicles they produced domestically between June 1940 and June 1941 IOTL for the ATL Barbarossa 1940.
Not sure how you're coming to that conclusion given the impact of the strategic air war in 1941-42, including the diversion of economic resources into air defense, as well as the impact of the blockade on the German/European economy. Rail construction and repair were also tied down managing the situation throughout occupied Europe and Germany and weren't simply free for the Eastern Front; in 1941 the need to divert resources to the USSR to deal with the situation actually had a significant negative impact on the economies of Germany and occupied Europe, especially France.
The draw of resources from the strategic air war in 1941-42 were miniscule to nonexistent. The British didn't even commence a sustained air campaign against the Germans until 1942 and even then it didn't reach levels that seriously drew on resources until '43. What's more, what raids did occur in this time period were rarely targeted against transport infrastructure or even much in the way of industry at all, tending to be much more symbolic or experimental (testing out new tactics, equipment, and bombing techniques) then practical. Hence rail construction and repair crews were hardly bothered by it nor were they bothered by the nonexistent need to rebuild the Western European railnet, which had been captured intact and already existed at standards similar to those within Germany. What hurt the Western European rail net in this period wasn't damage to infrastructure the need to divert looted rolling stock and locomotives... which IATL aren't available to the Germans, reducing their ral transport capacity further.
German trade per-war was not falling apart in terms of the import-export clearing agreements.
Yes they were. We've been over this: Tooze lays out in detail how German imports crashed in spring of 1939, with concurrent impact on German production: the Luftwaffe's aluminum access fell by 2/3rds and copper to a measly 1/5th. (Adam Tooze, "The Wages of Destruction," pp. 304-305). Overall German ammunition production had fallen to a mere 25% of 1938 levels by the summer of 1939, again, due to resource shortages. (Tooze, p. 314). Tank, artillery, and small arms production tell similar stories. Only the release of emergency strategic reserves of resources were able to restore the situation and those would have been exhausted by mid-1940, leaving the Germans with nothing left. The knocking out of France and consequent looting of her material stocks was hence a much needed reprieve. Not for nothing is the relevant chapter in
Wages of Destruction titled "Going for Broke".
If war is declared they could defer those payments for the duration of the conflict, as they were held internally by German banks
And their imports cease, since those payments were owed to foreign countries and they won't take kindly to Germany not fulfilling their agreed upon trade deals.
Axis minors were paid for their goods during the war, Romanian even held back oil until it got payment in the goods (weapons, coals, steel) it wanted. Switzerland and Sweden were paid for their exports, Switzerland through gold and other currency, Sweden with coal and other trade.
All at extortionate rates so far below the market prices they might as well have been nothing. The fact they were able to barter instead of having to actually pay with much in the way of actual money was purely down to the threat of force and the sheer military dominance over the continent the Germans had managed to establish in the aftermath of the Fall of France.
Certainly without conquering Europe they'd be in a worse position and have lower output compared to OTL, but you then have to factor in the other changes: no naval war, no inability to maintain global trade, no occupation expenses (need to feed and supplies the economies of included), no need to finance Italy's war effort, no need to fight Britain with all the expense that cost both to defend Europe against invasion/the air war/the war in the Mediterranean, no losses from fighting the Allies or Poland or in the Balkans, and so forth.
All of which were miniscule drains compared to the war in the east in '41-'42 and which certainly weren't more then the windfall from the conquest of Western Europe, which sustained the German war effort through the vastly more costly periods of 1943-44, when the drains from both the war against the Soviets and the other fronts were vastly larger.
IIRC something like >60% of war spending was on fronts other than the Eastern Front.
A number you pulled from nothing, particularly when it comes to the most critical years of 1941-42.
What problems were those exactly then?
Same as those faced in 1941: an inability to ship adequate amounts to cover all needs, requiring the Germans to be selective and prioritize what they shipped.
The Otto Program didn't cover Eastern Poland, it was the pre-invasion build up of their part of occupied Poland and was sufficient to cover all their needs, the problem was on the Soviet side of the border I don't know what being in a shooting war did for speeding up dealing with the logistics in Poland, if anything it only slowed down the build up, as the steel for it went into munitions and replacement equipment lost in France.
I never said anything about the Otto Program not covering Eastern Poland or not, merely observing that the resources devoted would not have brought up Eastern Poland. Certainly, Germany couldn't expend those resources on Eastern Poland without denying them to the build-up of the rail-net in western Poland, rendering the whole exercise pointless. Most of the need to replace munitions and equipment were trivial expenses, as losses in France had been very low and were basically paid for themselves by the profits of the early conquest with vast surpluses. That much of the motorization of the German railway repair corps that was managed to be motorized (which proved to be inadequate) was done with captured Western European vehicles shows that claim that it cost German rail crews more then they gained is frankly bunk.