should stop buying gas and coal from Russia altogethe
By the same logic, we should stop buying oil and gas from all countries that are dictatorships. Which, even if possible, would lead to a significant increase in heating bills for our citizen, thus making unfeasible. Trade with Russia helped eaasing tensions between East and West during the Cold War, and became an important bargaining chip during the negotiations for the withdrawel of the SU from Eastern Europe. And it remains one to this day, because it is one the most effective deterrences we have. Putin knows that he can not afford to lose it, so he will always take this into consideration, e.g. in his policies towards the Baltic states. I've read once that the Baltic states are prepared to destroy NSII if they are invaded, which means that Russia would lose billions, even if the West would still want to buy his gas.
Has anyone done a study
I doubt there are many projects that have been better prepared for this than NSII, precisely because the designers knew that this could be used as an excuse to halt the project. I recently watched a documentation about this. If there is a leak somewhere, the flow of gas can be stopped within a second.
reasonable that Russia and Germany
Do you think Poland does the same in case one of the LNG shipments have an accident, which unlike NSII, often travel through German naval territory? Of course not.