Methink that Stalin's fear of "United Anti-Communist Crusade" is the biggest reason which makes all those apocalyptic "USSR attacks this" and "USSR attacks that" scenarios ASB.
Yes, any bold move on Stalin's side without both Germany and Entente being busy elsewhere is unlikely.
Unlikely but not impossible. While the man had a lesser (but still substantial) dose of sheer megalomania than Hitler, he had an even higher one of sheer paranoia, and he was badly prone to underestimate his enemies' ability and determination to fight (Winter War, Barbarossa, Korean War). Therefore, it is perfectly plausible that he triggers a general European war (or more likely a World War since in any war between the Euro powers and the USSR, Japan is very likely to intervene with roughly equal possibilities to backstab either side) because he underestimate the capitalist powers' will to fight and/or their military capabilities, or he thinks they are going to attack anyway and therefore a pre-emptive attack is the best option. I freely concede you that this scenario is rather more more likely in 1942-43, when the purges, the modernization of the Red army, and Soviet industrialization, are all basically done, if a PoD somehow prevents Hitler from unleashing WWII.
Would Stalin attacks in 1936, France would still be in doubts about resurgent Germany, but, being pressured by it's own fears of new war, as well as British fears of "Red Menace", it would not protest much.
Especially because Poland and Romania are unlikely to stand on their own for too much, the 1936 Red Army is nowhere like its previous rag-tag 1921 incarnation. In this scenario, Germany is sharing part of the military burden that would otherwise fall squarely on the shoulders of France and Britain. Also because a sizable part of the British Empire's fighting potential must perforce go to man the Middle East/Central Asian front.
Yes, Czechoslovakia factor is interesting one. I believe that OTL Sovetization of Czechoslovakia was one of most stupid political decisions Stalin ever made. In any other reasonable realistic TL but OTL Czech were doomed to be Soviet pals.
This does not change the fact that in this scenario, their obvious alliance with Stalin would be just as stupid. It gives Germany good justification to scrap Czech independence with the support of the West, not just claiming Sudentenland as IOTL or satellitization, which would be the obvious result of the Western-German alliance, but the annexation which IOTL was what really turned the West against Hitler. They have just given Hitler a good argument why he cannot tolerate an independent Czech state on his border. Sure, the Czech army was good and Czechoslovak would give the Red Army a corridor to backstab Poland and overrun Hungary (which makes Romania's situation quite hairy). It is more doubtful whether it would be enough to allow the Soviets to overrun Silesia and Austria, which is what would really make things hairy for the *Allies. Otherwise, when the Anglo-French-German-Italian mobilization is done and ready for a counteroffensive, the Czech are politically and diplomatically in a world of trouble.
Don't count on it too much. IOTL Western Allies didn't give a rat's behind about fate of European Jewry (I mean, even if one is deaf and blind, everything was painfully obvious after Kristallnacht)
The Final Solution was not written in a secret appendix to Mein Kampf, although brutal separation of Jewdom from Germansphere was. For a long period, the default plan was "let's dump them in some forsaken distant corner of the world and forget about them". One of the main reasons it did not fulfill was that Germany was at war with the powers that controlled the seas. Here they would be wartime allies, or benevolent neutrals (America). The way is clear for the explusion option.
and they signed Munich agreement when Buchenwald was up and running, so Western involvement just prolongs "pre-extermination phase" a bit.
Up and running for the Nazis' political opponents, essentially. And in 1936-1938 Nazi concentration camps were essentially that, concentration and forced labour camps, not organized extermination engines. Big difference. No doubt that when this war breaks out, the French are busy throwing their own Communists in their own concentration camps like they did OTL while the USSR was Germany's quasi-ally.
It is very telling that even your imaginary warm and fuzzy Hitler isn't going to treat Russians as equals (BTW, what "non-Russian satellites" are you talking about in 1936? Balts are independent at this point and Ukraine, without Kresy being united with Ukrainian heartland, is pretty loyal).
I have no doubt that Stalin overruns the Baltic states the moment any capitalist great power intervenes on the side of Poland. I'm a bit uncertain whether Finland would be able to keep its neutrality for long, but otherwise Western intervention immediately expands the war in a ring of fire from Memel to Kandahar.
I have terrible doubts, that Ukraine, after the Holodomor, is going to be any loyal to Soviet butchers if given half a chance (i.e. if the German troops, with the Anglo-French in their midst, are obliged to behave gentlemanly when they show up in Kiev, so the Ukrainians don't get OTL tragic disllusionement).
They are not likely going to be treated as equals (BTW, there was a lot of folks around the world that the Anglo-French did not treat as equals in the 1930s-1940s, either, and Stalinism only treated everyone but its cronies and thugs at the same level of abject misery, when it did not targeted them for random extermination). The point is, if the Nazi can be coherced by the constraints of wartime alliance to go along with the plans for satellitization instead of extermination (an option that did exist in their mind, see Rosenberg's plans), living as a satellite of non-genocidal fascist great power beats living as a subject of a communist great power, b/c fascism is better than communism at making the life of non-scapegoat-minority average subject less miserable. The OTL non-Russian minorities seemed to agree, until the Nazi turned genocidal.
Besides, are you talking about the same Allies who pressured every dependent state IOTL (I'm talking Latin America and SA mostly) to refuse Jewish refugees entry? To put it simply, I see no reasons for Hitler's policy being any more benevolent than it was pre-OTL Barbarossa. And, with Barbarossa starting 5 years earlier in your dreams and Allies obviously trying to be as uninvolved in fight as they could... Yeah, this is very nice future for EE Jewry under the blind eye of Allies.
The British and French have plenty of poor-value colonies they can sell a valued wartime ally at discount price to dump its unwanted minorities in. They are going to roll their eyes while they do so, but they are going to humor the guy that is shouldering like 40% of anti-Soviet war effort, like they humored Stalin IOTL. Being kicked out of Europe is not nice, but surely beats the death camps by leagues. And a much more popolous Israel in some corner of Africa surely raises much less hardship for the world in the future. A 10-million Israel in some place less troublesome than Palestine would be a great asset to the world, besides avoiding a terrible tragedy.