Tamara, I much prefer “toe of the boot”. Don’t get caught up in the belief that if something is a calque from Russian it must be wrong. Some people make a lot of mistakes by trying to avoid calques.
This is a case where I think a Google count and analysis is appropriate.
For boot toe, I got 30,700 hits, but they all seem to be from product catalogues, and boot toe is usuallly a part of a larger compound in them, e.g., boot toe stretcher, boot toe clips, boot toe spikes, etc.
For toe of the boot, I get only 20,600 hits, surprisingly, but they are of a more conversational, colloquial, non-commercial nature: (a) The toe of the boot has a black rubber cap that also appears to be well sealed to the leather. (b) Stand up straight and push your foot forward into the toe of the boot. © Milly Mouse slid out of the hole in the toe of the boot.
For toe in the boot, I get only 1,020 hits, and they are of a different nature: A toe in the boot was used for the DNA analysis that identified the corpse. These examples usually involve a human toe that’s inside the toe of the boot, or, oddly, the “toe” of Italy.