A few comments...
You have quoted the JCS report twice, and while I certainly think that was relevant (they are, after all, the authorities on the subject), note that they are citing the number of DIVISIONS available, not the manpower available. Soviet divisions by 1945 were getting very thin in terms of manpower, particularly in terms of rifleman on the line. Given their losses from 1941-1944 (to say nothing of the bloodletting in Berlin in 1945), this is hardly surprising, and the significant number of Central Asian divisions (which Stalin did not trust) in the front lines by 1945, it isn't hard to see that the bottom of the barrel, if not being scraped, was at least being bumped up against. Keep in mind that the JCS was in the business of threat inflation, and their history of predicting the nature of their opponents (manpower resources, etc.) was not exactly without flaw...
You mention the capture by the Soviet armies or large quantities of military resources as both a basis for the war, as well as a way to sustain it. Given the very high quality of your other work, it is disturbing to see this rather naive comment. Large quantities of strategic materials (Soviet industry was heavily dependent on outside sources for many of these in 1945) are not lying around in depots in Western Europe, and after current stocks were exhausted, there would be big problems. As for military material, this isn't a war game where you capture supply points...the Soviets would have captured massive amounts of ammo that they couldn't use, heavy vehicles far inferior to their own (unless you see them switching from T-34s to Shermans?) and that most of their crews weren't trained to use, and a substantial number of entirely secondary resources that might be more help than a hinderance (troops leaving an advance to loot was a big problem in Germany during their advance in 1945). Even the things that they could use (trucks, fuel, and food) while useful, were not entirely fungible, and the number of trucks in particular wasn't nearly sufficient to resolve the big logistical issues that any Red Army advance was going to face. Railheads weren't going to magically appear (and trucks are not a solution to that problem), and the rest of the Soviet logistical network simply wouldn't be able to sustain constant advances. They couldn't do it in 1945 when they were much closer to their logistics net, they weren't going to have an easier time doing it through the blasted remains of Germany in 1946, especially when they had done little or nothing to extend their network.
I note almost no response to comments made regarding 'back door' attacks against the Soviet Union. The Pacific is quite vulnerable, but so is the far north, which would certianly put a crimp in your plans for Sweden. This is an area where the USN and the Royal Navy would be able to make their power felt, and the USN did have a history of 'demonstration raids'. These would not be decisive in and of themselves, but they certainly would have had the effect of tying down some of the Red Army and keeping Stalin looking over his shoulder.
As for nukes, you assume that the 'Fat Man' type weapons (Plutonium) were the only way to go, and that even in a wartime situation we would have kept building them no matter what. There is a HUGE difference between a 1946 where the US was at peace and a 1946 when the US was in an war with an enemy like the USSR, and pretending that there would be no changes is simply disengenous on your part. At the very least, 'gun-type' (Uranium) bombs would have been pressed into service quickly enough, and these were both lighter and much quicker to build. LeMay's comments regarding the silver B-29s (soon B-32s, and B-36s, though not yet) are well taken, but once again, wartime expedients (especially when we are LOSING...something that tends to clarify one's mind a great deal, and causes all kinds of expedients to be examined) would probably make that issue nugatory.
With regards to allies, the JCS notwithstanding, any supposition that the Soviets were going to have 85 divisions available from their allies is delusional. At the very best, it is possible that they (the allies) might not be a net drain on Soviet resources in 1946 (now 1948 or later is another matter) in terms of garrisons, etc. Since these allies lie directly athwart any conceivable lines of supply for the Soviets, there are limits to how aggressively the Soviets can conscript here, even if they were willing to try that.
I don't find it difficult to imagine a Soviet advance to the Rhine (in somewhat jerky stages) along with some aggressive use of intelligence assets to disrupt Western operations outside of the european mainland and of course France, where the communists would be doing everything they could to sabotage Western operations. Your analysis of air operations strikes me as spot-on for a short time at least (about 3-6 months, till aircraft arrive in quantity in the UK and Western France/Spain), but unless Stalin is willing to settle for that, the party will end for him shortly thereafter. The American military will take time to reassemble, but the dangerous parts (air power) will reconstitute more quickly than the rest, and while it may be insufficient to stop a ground assault at first, the Red Army logistical network will be hellishly vulnerable.
As for nukes being difficult to use tactically, this is a debateable point, and one that is by no means certain. Given the likelihood that just about ANYTHING might have been tried (wartime, after all), it isn't hard to imagine using 1 or 2 nukes on Front-level command/supply complexes, or large bodies of troops. The strung out nature of supply for the Soviets means that there would almost have to be vulnerable nodes, and this is the sort of thing that the West was VERY good at exploiting. Do I see air raids on Moscow in 1946? Not likely...but that wouldn't be decisive in any event. Stop the Soviets at the Rhine (likely) and the rest will come with time as the Western military gets back online.
