[YoungPup1977]

From the bottom of the VB you most likely can not determine if the tv valve itself is moving or stuck. Removal of the VB will be the only way to determine this.
As far as the number of rings showing on the plunger, you can push the plunger in until it gets spring tension which will show 4 rings outside of the VB. This is normal. With the plunger all the way out will show 6 rings. See pics.
So when you have 6 rings showing on the plunger, you should be able to push the plunger in to where only 4 rings showing without any spring tension.
Since you have the pan off, With your tv cable hooked up is your plunger pushed in with how many rings showing. Let’s start here.