Questions regarding the Eye tracking data measured in Quest Pro

I've only recently got my QuestPro so still new to this but from what I can see so far, the eye tracking API is very much focused on automating an avatar's eye movement rather than being used for gaze detection. Such a shame as I was hoping for gaze UI events being available and object detection (as you are doing). It's not to say it can't be done. 

If you look at Common Issues#4 (in the documentation you're probably looking at) you'll see that you can do a raycast from the eye transform:

"Can I use eye tracking to highlight certain areas of interest in my scene? Yes, you may do so via raycasting driven by the eye transform’s forward direction. Since the eye might change direction rapidly, it might be useful to apply filtering to the forward vector used for the raycast"

The last point is important as depending on how far your ball is from the player it might be hard to hit it with a single raycast. (From memory, when I last did this on Quest 2 using just a perpendicular raycast from the HMD, I used a boxcast to make hits more predictable/reliable)