That's right, Clint points out that you have measured the screen current directly, even though a little bit indirectly and it does check out, 2 mA is alright. Better numbers will help. Because right now the cathode current does not equal the screen current added to the plate current. Until better numbers are found, it looks like more current or electrons are entering v5 at the cathode than electrons are leaving v5 at the screen and plate combined. And that would make problems for the fuse.