Where are the Wallies going to give supplies from? Who is in charge of the Ural government?
That's an answer for the OP to figure out.
How are they going to be supplied in Japan steps in in the East?
Japan is already committed to war with America. Even if they do move north to take apart, all of that is gonna go away when the US defeats them.
How are they going to deal with the major famine that will result from losing at least half of their LL supply hubs and all but their Central Asian farming (which was totally inadequate to supply the amounts of people evacuated to the Urals IOTL)?
Well the overwhelming bulk of the Soviet civilian populaces food in 1942, 1943, and 1944 came from private gardens. Partisans also established their own private gardens in their hideouts.
Plus the Germans would likely be able to use lots of persistent chemical weapons without detection by the West in major problem areas.
How are the Germans going to avoid detection? There will be plenty of people escaping into Siberia and south into Persia and they'll be more then happy to inform the WAllies that the Germans are using chemical weapons.
Assuming revolts succeed without major external support, which is unlikely as the history of US slave revolts demonstrate (which were only as successful as they were due to poorly armed musket armed militias and heavily outnumbered whites on plantations being the only guards).
And who do you think is going to be more numerous once the German troops leave? Even in the camps, the Kapos were backed up by the presence of German forces (not necessarily on-site, but close enough to act as something of a rapid-reaction force).
Sure, as it would be in the labor system in the East.
Which would further degrade the economic value of the territory over time. Mass murdering your work force isn't very conducive to getting anything worthwhile from them. The Germans ran into this problem with their slave labor IOTL. Running genocide may be all very useful for eliminating resistance, but in terms of extracting economic value from a already devastated territory it's a non-starter.
That's not likely to be a steady undermining, its more like a planned cost, because resistance would be minor and they'd perfect the system over time. As it was the slave rebellions in the US were never even a minor disruption to the economy.
Of course the major difference between the slave system is that the slaves were working in a established economic infrastructure, not something which has been devastated by a destructive invasion, and their rulers were still (in the final analysis) more interested in extracting work from them then killing them all in pursuit of some crazed racial vision (which, incidentally, still left the African slaves with rather something more to lose then our hypothetical Soviet counterparts). Oh, and the entire system ultimately proved to be economically noncompetitive to wage-labor capitalism.
As for bombing, after a lot of false starts, it did defeat the Germans. Per the Germans, their economy was weeks away from total collapse before the Allies crossed the Rhine due to bombing. The armies got the credit because they did conquer the territory, but German military production was headed for complete collapse regardless of events on the ground in Feb-Mar 45.
Except it didn't, although it could have. The point at which strategic bombing pushed the German economy to collapse was in the winter of 1944/45... at which point the Reich was collapsing anyways from the defeats it had suffered in the ground war. Saying that the German economy was "several weeks away from total collapse before the Allies crossed the Rhine" doesn't mean much when the German armed forces had practically already been broken and all the rest was basically a expensive and glorified but bloody mop-up operation.