My TT is in storage for the winter still, so I cannot just go look at it. As I recall your threshold looks like mine.
My strut lost its strength I bought a new strut on amazon, dealer told me to buy a 20 lbs, 20 inch unit. I think it is too strong, I would preferred something like a 15 lbs strut. I used my existing ball, I just unthreaded the caps on my new strut and used the old mounting hardware.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
A couple years ago I also had the ball come out of the threshold. I recall it was an easy fix after sitting looking at if for a few minutes, but I do not remember what I did.
If the ball is not damaged, you an install it in a new location in the threshold or fill and fix the current location (that is what I did).
Good luck.
FYI, I'll be picking up the TT from winter hibernation in a couple weeks. If you do not have it figured out, ping me after April 3rd.