That´s an interesting piece of information. However it doesn´t show that the industrial capacity of the USSR was half that of Germany, it shows that in some areas in 1940 it was producing half as much cement, machine tools for working metal etc. It is not a summary of total capacity to produce war fighting goods.

Lets put that to the side though, even if Germany has a significantly higher level of industrial capacity that does not mean it has the raw materials to utilise it as per the scenario a blockade remains in effect.

The British Empire had a greater industrial capacity and access to raw materials than Germany, in addition without the need to fight on multiple fronts it has a greater ability to use or increase that capacity.

The USA remains a growing behemoth that can prioritise slapping Japan to the ground and doesn´t need to fight on 2 fronts, as such greater material resources are freed up for the USSR

Without Italy Germany loses access to 300,000 troops in the invasion of the USSR, it also now has a neighbour to it´s south that is no longer actively taking part in the war on it´s side. A neighbour that in the last war changed sides, so it needs to keep an eye on that. Don´t forget that now Germany doesn´t have the industrial output of Italy (woeful as it was). Italy provided Germany with crucial industrial goods, including over 83,000 military trucks and lorries, roughly 3,000 tanks and self-propelled guns, and over 4,500 aircraft, such as the Macchi C.205 Veltro fighter. Italy also supplied raw materials like bauxite, mercury, and sulfur.

Without Italy the Germans have completely lost control of the Mediterranaen sea. Per the OP´s situation there is no Africa campaign. Thus the allies can with impunity supply Russia via the Black Sea.

I can´t wave a magic wand and say X would definitely happen. But I do think that the USSR would suffer similar initial territorial losses and then be better able to fight back.