Awww *hugs* I can totally sympathise, Squid is the same way with cats that come into the yard.

Our yard is fenced into three parts, one for the dogs, one for the chickens and a bit in the middle for plants, that's where the cats like to sit, and even though the fence is high, I'm worried that one day Squid will be able to get over it, and I know he'd kill a cat if he got to it. When I see the cats there, I have to go outside and shoo them away, which I feel guilty for, but at least it stops Squid from getting to them.

regarding the kitten in the tree. Assuming it's not a really tiny kitten, which it doesn't appear to be from the pictures, it should make it down on it's own. You could maybe put some food down to tempt it, or try calling it again. If it doesn't come down within 24 hours, it might be time to send someone up with a ladder, or as a last resort, call the fire brigade.

I hope it comes down soon