See: https://www.nalog.gov.ru/eng/tax_statistics/rbr/ 40% is "mineral extraction tax". I think official Russian government figures are trustworthy enough?

The power of Siberia pipeline supplies energy from fields close to China in eastern Siberia. It can not be utilized to divert gas from western Siberia that is currently send to Europe. There are literally tens of thousands of kilometers between those.

Industry demand for gas can be much easier substituted for other energy sources and/or the end products imported from other countries.