It wasn't experienced pilots that was the issue, it was raw materials. The whole island nation thing. Yes, the British were making better uses of manpower (radar made up for a lot) but they still were unable to maintain the constant repairs of air bases and radar installations long term.
Again, incorrect. German raids generally only knocked out air bases for a few hours on average and their repair mainly consisted of filling in the bomb craters. The raids against the radars were even more drastic failures, although this was because the Germans simply didn't actually pay them any mind.
Also, it wasn't so much the slave labor as it was executing the entire native population who, at the time, saw the Germans as liberators. Stalin, a few years earlier, had deliberately cut much needed supplies leading to the starvation of thousands. I'm also going to contest the whole 'made good use of slave labor'. They didn't.
While it certainly helped, the Nazi's were explicitly working them to death, which is in no way sustainable and would have (and did) hurt them in the long run. Using slaves to make goods only works as long as the slaves are alive, and the Germans made no effort to keep them so. This constant turnover resulted in needed more slaves to keep the industry running, taking manpower and transports that could have been better used elsewhere tied up in maintaining the slave population.
And it was always going to be so, given how Nazi ideology worked. There was no alternative source of labor available and to actually feed those people meant taking food away from German citizens, which was unacceptable. The Nazis just applied capitalism to slave labour, with races as the brand names.
The Russians the Germans first 'liberated' saw them as such. They would have willingly contributed to the German war effort, had the Nazi's not slaughtered or enslaved them all.
The only places which welcomed the Germans on a large-scale were not any parts of Russia proper, but rather those parts which had recently been annexed into the USSR since 1939. Further east, the Germans were met with apathy at best.
Not to mention that once again this misses what the entire point of Barbarossa was. Hitler's goal was to secure industry and raw resources for the Reich, but before the invasion the Wehrmacht's economics section pointed out that even if conquered, the Soviet Union would actually be a net
drain on German resources for years to come, particularly after the ravages of war. Simply feeding the conquered Soviet population would be a huge draw on Nazi stocks and transport. Hitler's solution was as simple as it was immoral. Kill the Soviet population. In terms of logistical support and such, the Germans probably saved a lot more doing this then it cost them (in fact, they definitely saved a lot more: they didn't have to ship any foodstuffs to the soldiers since the troops just took from the Soviet population).
The atrocities perpetrated on the Soviet citizenry were not some regrettable unpleasantness the invasion could have done without. They were a key factor in making the whole venture worthwhile to Nazi Germany. Without them, the invasion loses any economic legitimacy. And it will also give a morale hit to the German soldiers. Fact is that racism, and race-based exploitation, are very effective vehicles for conquest. If you try to treat everyone fairly and equally, then you're gonna run into a LOT of problems trying to build your empire. It gets worse if one of the chief reasons for your expansion is to steal resources from others, as was the case with Nazi Germany. Then you need a very good reason why your people deserve other people's stuff more than they do themselves, and racism is very good at providing that reason.
This isn't just talk. People need a reason to lay down their lives for their country, and states that are unable to provide sufficient reason often fold under pressure. Fascist Italy is a good counter example. Although Italy certainly had some of the same racist dogma, it wasn't as pervasive or as popular. Once the going got tough, the Italians asked themselves just what the hell they were dying for, then threw in the towel. A country doesn't fight to the bitter end for nebulous reasons. The Germans fought incredibly hard in WWII because they had a pervasive ideology that made sense to them. That ideology told them they were better than everyone else, deserved to be on top, and were justified in killing anyone else until that became a reality. It was incredibly racist, but it worked.
What is going to happen is that you have somewhat less motivated soldiers ("Why are we invading these people?"), little change to the opposition of the occupied people ("You launched an unprovoked attack and conquered us!"), and a much weaker war economy ("We can't take those inhumane emergency measures! Poles/Jews/Ukrainians/Russians/Belorussians/Roma/jesusyouaretryingtomurderalotofpeople are people too!") In all probability, it costs the Germans the war
faster.