It's not sustainable in the long term, but that term is actually quite long. This isn't going to be a short or medium term crisis. It's going to take years, and a lot of consistent political will. I hope we're up to it.
I'm not so sure about that. There were a bunch of news outlets warning that Gazprom is on the brink of a massive default. Gazprom, of all companies.
If the company that subsidizes Russia's ruling regime can't make their payments in spite of sitting on a huge pile of oil and gas, that does not bode well for Russia's economy.