something chased him.

I am so glad you found him. If you still let him out, in the future, it might
be a good idea to provide a high rescue place for him.

Some people in our area create climbing havens for their cats. We have a natural 45 degree angle tree that leads to the little roof on our porch, which leads to the rest of the roof. Our old cat can't do this anymore, but the other two do. They run up and hide on the roof if they spot danger. I even put a cat door in the screen in my bedroom, and they go out and enjoy "out" without having to really be "OUT" if you get my drift.

This is a picture of Oreo on the roof just over the study, where the main computer is.
Our home has many small gabled spots...and Oreo walks all over and watches the yard from there. She is very muscular and athletic for a cat.

This could be a good project for your son to design. I have seen some on pet shows that were amazing. You'd just need one that serves the purpose for safety.

I have to wonder, if he has poor eyesight still... that is also something to think about.

And that is TOO much that you found soulmates for the guys. How karmic is that? ! So what are you going to name these new ones? It is also ironic he was lost on the full MOON. And now you have a new "moon" kitty! Are the new gals the same color gray? Could they be related?

Quite the adventure, I'd say....