Hello there, I am so very very sorry for your loss, I know how you must be feeling,
We have a cat like you had called Tomson.
He is partially ferrel too. Likes to be out all of the time.
He is friendly enough though but you still have to be careful.
He spends most if the summer outside, but knows where his bread is buttered on the inside in the winter.
We worry just like you but are fortunate in as much that there are farmlands and fields behind us.
Where we live though, there is still a chance he may be poisoned or accidently shot by hunters.
We also have anorher stray called PC.
Fortunately he is a very domesticated cat as when we found him as a tiny kitten we actually trained him to walk with a lead because of this fear we have with Tomson of losing him.
He spends more time here then he does out.
This could be an on going idea for yourself should you get another kitty.
I really do hope you feel better soon my lovely xx