I think people get the Nazis all wrong. They were mad, yes, but they were the kind of mad which is a lot scarier than anyone with a carving-knife and a distant expression: they had fundamentally sick, wrong, and anti-human ideas underpinning their philosophy and worldview, but they were rational and functioning people who were able to put into practice plans to achieve their goals. Theirs a reason they ended up giving the rest of the industrial world a run for its money rather than giggling in a maximum-security cell.
We know, in hindsight, that it was overwhelmingly improbable for them to win the war. That doesn't mean they were on a death-ride: each decision they made had some kind of logic behind it, at least in their world.
To start with: Slavs. I think the problem here is that we identify Nazi social-darwinist racism with modern in-one-country and generally American racism: that is, race is the thing and the whole of the thing; if there is some sort of hierarchy, it begins and ends with race.
In fact Nazi ideas were based on the idea of a worldwide struggle for survival among different peoples. They believed in a racial hierarchy, and for instance they obviously regarded black people as 'semi-apes' and at the bottom of the heap. But they didn't set out to persecute black people - the local authorities did harass and discriminate against the 'Rhineland bastards', but black Berliners, IIRC, just slipped under the radar and even served in the Wehrmacht - because black people weren't the goal of their plan for colonial power.
The Slavs were believed to be sub-human because they were in the way. That's the important thing. The Czechs, the Poles, and the eastern Slavs were on territory that Germany urgently needed to dominate if it was to achieve American economies of scale and hence secure itself as a world-power; so they had to go. But even anti-Slavicism wasn't consistent. The Poles and Czechs has been Menacing Germandom for decades in lurid imaginations; the 'Russians' (Belarussians, Ukrainians...) were the commie masterminds. But the Nazis didn't treat Croats or Bulgarians with much more contempt than they treated Romanians and Hungarians.
The Slovaks and Croats were allowed to set up states. Ukrainians who wanted to set up a state, even though this put them in a corner with the Nazis against the Soviets, got shot: the Nazis couldn't allow east Slavs to dream of ruling themselves.
It is well-known that Hitler ranted, in his last days, that the German people deserved what they were getting; and I recall hearing from somewhere that he wondered aloud whether the 'Russians' had in fact been the master-race all along.
Now, though it connected to a long strand in German and European history, and satisfied the need for an enemy about which to cause panic, the hatred of the Jews was certainly not physically necessary to the Nazi plan - though intellectually it stood at the heart of a worldview in desperate need of enemies.
But the Slavs were the enemy because they needed to be exterminated, and you could tell they were inferior because the superior Germans were going to exterminate them. Snake eats tail. A regime less homicidally anti-Slavic - all right-nationalists in Germany were more-or-less anti-Polish and anti-Czech - has no reason to invade the Soviet Union or to base its policy on the ultimate necessity of so doing.
The war-economy. I am much less able to spraff about this off the top of my head, but the essence of it is that Germany was already astonishingly succesful in mobilising an industrial and resource based dwarfed by that mobilised against it - and it accomplished that only by the extensive use of plunder and slavery. It wasn't as if the Germans had factories working at half-speed. The Wages of Destruction by Tooze is an instructive read.
Weaponry. All this rests on hindsight. In 1939, for example, everyone assumed that u-boats were at most only as important as Germany's surface commerce-raiders - and to be fair, without the ports of the grossraum their range was extremely limited. It was the rapid conquest of western Europe that made the u-boat threat urgent. So why should the Nazis have invested more in u-boats before? They already made naval plans which were simply too grandiose to reconcile with the more urgent land build-up.
Treaties with Britain. Have we any specific examples? I think Hitler's Anglophilia - a grudging respect for the arch-imperialists that gave way to a mix of fury at our determined opposition and contempt for our umbrella-twirling and willingness to mortgage away the empire - is badly exaggerated.
Invading the USSR. Well, what was the alternative? A continuing war against Britain with the industrial capacity of the United States hovering behind it, allowing us to gain larger and larger advantages in the air while the Germans much around in Africa and wait for Stalin to decide that he's had his fun watching the capitalists tear into each other and turn off the supply-tap?
The Germans had backed themselves into a corner, and the only way out of it was to defeat the Red Army in one go. In retrospect, of course, this was a pretty crazy thing to bank on. But who had expected them to conquer France?
After all, they did inflict the greatest land military defeat in history on the Soviets. It just didn't do them any good in the end.