For sanctions advocates in the West, the steep slide in the value of the ruble this year is a clear sign that the economic penalties imposed on Russia over its invasion of Ukraine are making an impact. They say the Group of Seven (G7) countries should strike while the iron is hot and lower their price cap on Russian crude oil exports, now at $60. The goal: Tighten the choke on the Kremlin’s revenue and force President Vladimir Putin to choose between economic stability and military spending. Russia’s central bank hiked interest rates by a massive…