what metals are in a crt gun

Hehehe the only poisonous gas inside the vacuum of a crt would be when you are watching a WW1 trench warfare documentary on the TV you are about to scrap

Another thing to keep in mind is that CRT's are designed to contain the vacuum, they are actually more stable and safer to handle with this negative pressure intact. There is only a small amount of vacuum inside them, and snapping the gun off the end tends to weaken the integrity of the whole tube by creating fracture zones from the sharp edges left behind.

Think about it this way. Take 2 glass bottles, snap the neck off one of them. Now drop both onto a hard floor from waist height, there is a much greater chance that the unbroken bottle will survive the shock and stay intact. But the pre broken bottle will almost always end up in many pieces around your feet. This happens because of the sharp edges left behind from the initial break, which leaves concentrated stress points, that the cracks can easily migrate from and along.

No one needs a cut from glass that has freshly exposed edges of the metallic oxides on it.

There's a lot "going on" inside a working CRT. The metal Cesium is not! Though it is used in other vacuum tubes.