I'd love to find a 21AXP22 for my CTC-4, but they don't grow on trees. Meanwhile, a glass CRT lets me watch the set. Without viewing two CTC-4s side by side (one with 21AX, the other with glass), I'm not sure my uneducated eye could tell one from the other, anyhow.
Sorry, I don't have a good guess about the orange discharge inside your CRT. What's the condition of the CRT's aquadag coating? All in good shape and securely connected to ground? Does the dancing glow move in concert with arcing sounds? Or is completely independent?
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html