On lend lease food....

As far as I know only about 10% found it's way to the military, as naturally they were already being looked after first by the Soviet government, and the civilians had to suffer, lend lease would have no doubt saved many civilians an empty stomach.


On aluminium....


In this timeframe, Alcoa (US aluminium company) had a near-monopoly on aluminium production in the world due to lack of bauxite deposit discoveries in the rest of the world. So yes, aluminium was in short supply everywhere, and so USSR used to buy aluminium from the States for hard currency and would continue to do the same without lend-lease. In 1941 USA actually was behind on deliveries of materials ordered by USSR before the war. USSR did not have a lot of hard currency, but it had enough to buy strategic materials. Without lend-lease, USSR likely would have to raise some more currency ie by selling its gold reserves. Tough, but not devastating.

The main use of aluminium is in aircraft production, USSR partially fought aluminium shortages by designing equipment which used it in minimum amount. So most of USSR fighters were made mostly of wood (which is not necessarily bad - so was Mosquito - but it limited their tactical capabilities). So aluminium shipments were important - but not to the point where there were absolutely no alternatives to imported aluminium.