localized weight units

For kg, you can replace it by overriding it like that in the translation override:
KG="кг"
We'll add that to the Russian translation file so that it's like that by default. Would you happen to know the other symbol translations in Russian so that we can put them in the translation file too ?

For the / between the price and the weight unit, we didn't know that this would be a problem in different languages, so it can't be done via a translation override.
You will have to edit the file "listing_price" of the view "product" via the menu Display>Views and change the line:
echo $this->currencyHelper->format($weight_price,$price->price_currency_id).' / '.JText::_($this->row->product_weight_unit);
to:
echo $this->currencyHelper->format($weight_price,$price->price_currency_id).' за '.JText::_($this->row->product_weight_unit);

Note that this line is present twice in there so you will have to do the modification in both places. We'll look at adding a translation for that in next release.