The number of sorties of the Lw fall not because of the vvs. Already by late 1942 several fighter and bomber units left the eastern front for the North Africa. In 1943 home defense also required units from the east.
I don't disagree that redeployments forced on the LW diminished the strength they could deploy to the east. I thought I was at pains on several occasions in my discourse to say, in effect to say that it was beyond the capacity of the VVS to achieve outright air superiority over the axis, but for much of the middle part of the war they actually did not make that one of their central goals.
However it is a greater piece of misinformation to claim that the LW sortie rates dropped solely because of falling numbers and redeployments. In actual numbers from July 1942 to May 1943, the numbers of Axis a/c deployed in the east dropped slightly. According to Hardesty it fell from 2900 to about 2500 (including the satellite axis) with the greatest losses occurring in LW fighter deployments (dropping from 859 to 615, including their fighter recon units), which is important, but does not explain the drop in sortie rates. You need to take into account the readiness rates, which fell from a high of just over 70% in June 1942 falling to under 31% by the following April. There was a partial recovery from late April through to Kursk, climbing to averages of over 50% for that battle, before falling away to a more or less constant of about 45% for units deployed to the front for most of the following year.
The generally abysmal serviceability rates on the eastern front arise primarily from the following factors
1) The weather
2) The poor logistics that bedevilled the Axis forces on the eastern front. Though this improved slightly as the supply lines shortened, it was never fully solved, and certainly in March 1943 was a major problem still . Even as late as march 1943, only 37% of required trains were reaching the eastern front
3) Consistent mismanagement by the Axis leadership as they continued to unneccessarily overuse their available airpower, forcing it to run up and down the front, fire brigade style without proper rest or refit periods and without adequate training programs in place, at the front, so as to bring new recruits up to standard.
4) Finally and probably the least important of all, the massively expanding numbers and capability of the VVS. In June 1942, the VVS strength stood at 3300 a/c, including about 1000 deployed to the far East. By the following May, its strength had risen steadily to about 6700 a/c.
The second factor was fuel . Already before kursk fuel situation imposed limitations on number of sorties. In several autobiographies of german pilots from both bomber and fighter units, report that they were taken "days off" because of lack of fuel. He177s were bombing on the eastern front,in early 1944 ,almost with no losses to fighters and stopped simply there was not enough fuel for them. VVS was unable even in 1945 to stop the schlachtgruppen from their missions..
The fuel shortages arose for two reasons, partly because of strategic shortages, but this was a minor issue for the eastern front. overwhelmingly the dominant reason for fuel shortages at the front was the break down in the supply chain. No enough rolling stock, too few rail lines repaired, plummeting MT numbers, sheer overuse and misuse of LW reserves were all to blame. there were a combination of Soviet and VVS actions that contributed to that....probably most important being the activities of the partisans, but also the interdiction successes of soviet Long Range Aviation (ADD). You mention the inability of PVO to intercept the German attack groups, which I will deal with in a minute, but in saying that fail to mention the equal, and more disastrous failure of the LW to deal with these rear area interdiction efforts against them
Now with regard to the absence of losses amongst the LW bomber groups. perhaps. but neither was this a priority for the VVS. Their primary mission was to protect their own bombers for long enough so that the mission could be completed and the breakthroughs on the ground could be achieved. These are taken directly from Novikov himself. STAVKHA certainly wanted to inflict losses on the LW, but the best way to do this was to achieve breakthroughs with ground forces and then overrun the rear areas like airfields. In 1943-4 the Soviets were immensely successful at this....what was the effect of the LW bombers in this period. virtually nil …..
As far as your final comments, I agree that not too much weight can be given to an "order" not to engage below a certain altitude. There also was no equivalent order for the VVS to go above that height. however, fact remains that VVS fighters, particularly their later types enjoyed their best performance advantages at these lower altitudes . Fact also remains that many VVS fighters were forced or ordered to fight above these altitudes. the premise on which this discussion is based, is that virtually all Hartmanns victories were made against fighters. Since we know that Soviet ground attack a/c heavily favoured attacks at zero altitude, it at least seems reasonable to argue that he tended to fight those fighters of the VVS providing topcover...ie above 5000.
As for your claim that over 5000 VVS fighter were deployed against Courland, I don't think so. In the whole fronts deployed in Bagration, which led to Courland, there were never more than 4000 VVS a/c, stretching from Pripyet to the Baltic Coast. In Lithuania, there were never more than 1000 aircracraft until very late.