Leoreth, that's not entirely true about the Lebensraum. By the time Barbarossa kicked off the Germans had pretty much all the Lebensraum they needed. It was estimated that they'd need about a hundred or so years to populate it with 'aryans' and to tap into the resources of the Reich's newly acquired territory. And IIRC those were official Reich estimates. In other words, they had bitten off just a little bit more than they could chew, and they were probably be willing to pull out of some of the occupied countries in case of a peace agreement that guaranteed them their (as already mentioned, pretty spacious) Lebensraum. The Germans would've been indeed more than happy to sign peace with the Brits and call it quits, but of course nobody would let them. Nobody but Hitler had anything to gain from a peace treaty at this stage. The Soviets were basically waiting for Hitler to try and land on the island (which was not gonna happen) and then stab him in the back (which was gonna happen, if Hitler hadn't done it first). Stripped down to the bones Barbarossa was a daring preemptive strike on the Red Army.
On a slightly related note to the bolded text I was reading Anna Reid's book on the siege of Leningrad recently and it was quite chilling to read the section where she describes the German plan for what they would do if they captured the city. Halder for example noted that in July Hitler had decided "to level Moscow and Leningrad and make the uninhabitable", thus "relieve us of the necessity of feeding their populations through the winter".
A planning session in September also ran through a series of options about Leningrad (apart from the bits I have added in brackets to point three and point 4 being summaried these following points are copied straight from the book)
1) Occupy the city, in other words proceed as we have doen in regards to other large Russian cities - Rejected because it would make us responsible for the food supply
2) Seal of the city tightly, if possible by an electrified fence guarded by machine guns - disadvantages: The weak will starve within a forseeable time, the strong will secure all the food supplies and survive. Danger of epidemics spreading to our front. It's also questionable whether our soldiers can be asked to fire on women and children trying to break out
3) Women, children and old people to be taken out through gaps in the encirclement ring, the rest to be allowed to starve (this option basically consists of the evacuated population being spread out across either Russian or German territory). In either case there remains the disadvantage that the remaining starving population of Leningrad becomes a source of epidemics, and that the strongest hold out in the city for a long time (note the lack of consideration for how the dispersed population would survive the freezing winter and/or how it would feed itself).
4) Leave at least part of the problem to the Finns.
The conclusion it came to was basically to tell the world that since Stalin treated the city as a military objective, so would they. Once it surrendered the Germans would offer to invite the American government to transport the population to the USA under the protection of Red Cross transports - an offer they accepted would be nothing more than propaganda. Whilst this was going on the city would be bombarded and civilians would be allowed out through gaps in the line. Anyone left would be driven out of the city in the new year into captivity, then the city would be wiped off the face of the earth with explosives.
All of this might sound fairly normal fare coming from Hitler, Himmler or Goebels. In fact this was a planning meeting of the Army's High Command. The wording lacks his particular brand of hate, but it matches his conclusions, mirrors his uncaring attitude to the civilians and reflects the same curious mixture of cynicism and impracticality that was such a feature of the Nazi party.
Nor was the Army the only ones to get in on the act of trying to be more brutal than Hitler. The main objections of a Naval liasion officer attached to Army Group North were on the grounds of practicality (it's hard to persuade even the most brutal of people to murder the unarmed in large numbers, plus we could really use those nifty dockyards when we really have to go hammer and tongs with the USA) and concern that the action would "let loose a worldwide storm of indignation which we can't afford politically". He also suggested trying to get Britain and America to evacuate the population by sea (and when they reject the idea blame them for what follows), although quite how he thought that would have worked is another matter.
It all serves to demonstrate that whatever plans Hitler did have for a post-war Russia, they were deeply unpleasant whether Germany kept hold of most of European Russia or not.
To me it rather sounds like that Hitler - out of despair over the failed Operation Barbarossa - fantasied about an alternate reality where he and Stalin were buddies. Which is typical for Hitler. Fantasying about things that are not.
