my interpretation of the strategic air war is that both sides have a key resource.
For the allies that is morale as usually they have the pilots and planes to keep the bombing going (ok they can be short of some national pilot groups and before the B-17G arrives) and for the Germans is trained pilots (again you can run out of some fighter types but usually can work around this).
Why? Well its low morale that forces the Allied player to stand down bomber squadrons and at a critical point you need to stop everyone or risk just flying in small numbers. For the axis player the critical pt is when you can no longer rely on trained pilots to fill out your fighters - after that your experience levels go very low and you lose a lot of air battles.
So to 'win' as the German you need to inflict max morale damage for minumum actual pilot losses. In truth, what you need to do is to nurse your fighter pilot cadre as late into 1944 as you can but at the same time slow the Allied bombing campaign.
So, agree partly with the above. Flak is a good compensation as its damage inflicting (=lower morale) and its far better to engage with your fighters en-masse rather than spread around. My view is I move them around and if I miss some raids that is a fair trade off for when I guess right.
I'd disagree about abandoning the Ruhr with my fighters (agree totally about getting out of France and Benelux). Its not till early-44 that the Allies have good fighters that can sustain operations over the Ruhr (the 1943 British fighters can't manage this) so you are not going to be beaten too badly. On the other hand as an Allied player, if offered the Ruhr as a free target I'd take it and just bomb there. There are enough VP on offer, plus other strategic targets, to make that attractive.
Small things to watch. Allied fighters on direct bomber escort tend not to inflict too many outright losses on you ... and you can cope with morale damage better than the allied bombers. Allied fighters on an AS mission will be hunting your fighters and you can't trade off these losses. So once you see this in the combat reports, thats when I'd pull back from the Ruhr. Its a good indication that the Allied player has both volume and the better 1944 fighters in operation and can spare them for aggressively hunting you rather than protecting their bombers.
You will need to rethink the defense of the Ruhr from Spring 1944, at that stage I would pull back, but also at that stage the VP multiplier for bombing is on its way down. Also you are then managing the last stage when the Luftwaffe has some threat. By late 44 either your experience is gone (pilot losses) or what you have left is pretty redundant (sheer number of allied planes, low VP for bombing, allied airbases in NE France etc).
The standard advice to run down your NF formations and flip the pilots to day fighters is sound. Its linked to the lack of targets really, by mid-44 Bomber Command will not have much left to hit and outside OBOE its actually not that effective. So your NF become redundant while you still need day fighters.
I agree with your take partially. However in the first 20 or so turns of the campaign you can attrit WA bombers (US ones at least and see less and less of them flying because they don't have an unlimited supply and almost all their groups fly either the B-17F or the B-24D which are out of production at that time. Plus it takes time to get a bomber group up to full strength even if they have the planes in the pool, so there is also that to consider.
Using flak is really important as it helps damage morale and increases operational losses by quite a lot. Moving fighter groups is also very important as you said. Sometimes you miss some raids and sometimes you catch some, it's the way the game goes. But the ones you tend to catch inflict serious losses on the enemy and curb your own.
I disagree on the Ruhr topic. A good WA player can have enough fighters flying AS missions over the Ruhr to damage the LW by a huge margin. In the end you are simply losing pilots by engaging in a head to head fight that you should avoid until 1944 comes. Bombing the Ruhr every turn as you say (if you notice that the enemy isn't flying any fighters) will not be very effective because of diminishing returns. After you have bombed all the factories to around 80% damage after 2 turns,you are doing an overkill if you keep bombing them because:
a) those damage numbers will only go up by a small margin
b) to the German player, a 80% damaged factory and a 100% damaged one are still the same in terms of productions. They will not produce anything.
And as the Germans you can sit your fighters back and let the pilot pools build up. The industry hit will be substantial no doubt but it will not be enough to induce huge shortages.
In my GC game against Hghx-0 he is using P38s massed with bombers everytime he attacks (and he is attacking deep into Germany before 1943 has even ended). So I'm constantly seeing 300 WA fighters escorting 600 bombers deep in Germany. If I even tried to defend the Ruhr those fighter numbers would probably double. That is a good way to completely destroy the LW in one week or two. So I have chosen to gather my fighters and try to guess where he strikes. I still take heavy losses but nothing like what I would take if I had intercepted such huge raids with say 300 LW fighters.
Now if the WA player has not yet figured out how to use his fighters then of course you could defend the Ruhr but I find it hard to believe that WA players won't realize that they can pull P-38 groups from Italy or fill up fighter groups with P-38s sitting idly in the pools and throw them at the Germans.
Pretty much agree with everything else you said. One must take into account the type of player they are facing and the way they utilize their forces. There is no "best way" if you will, only a best counter to what the WA player throws at you.