Welcome to the forum.
It is likely that you have an "Orphan," out at the end of the Timeline. This ARTICLE will give you background, and tips.
Also, some Export/Share choices will just handle the WAB (Work Area Bar) setting, and some will always do the entire Timeline, regardless of where the WAB is set. One also must limit those Exports/Shares, that accept the WAB by setting to Export/Share just that.
P.S. I've tried using the (extension?) tool (red with black arrows) to "pull" the video to the right, but that does nothing.
Not sure which Tool you are using, or how you are using it. Can you post a screen-cap showing that Tool, and explain how you wish to use it, in a bit more detail?
Press the backslash [\] key. This will adjust the timeline to show the whole project so you can see if there is something unwanted towards the end. It also makes it easier for you to see where your WAB starts and ends.
To reach the orphan (if that's what it is) use the PageDown key to move forward. If it goes beyond your expected timeline end you can then zoom in to find and delete it.
Insanity is hereditary, you get it from your children