Egyptian Mau kittens & cats in Inverness, Florida

I have 3 other cats, a male and 2 females, who all get along. Due to his age (he's12), I thought Chui would be calm enough and therefore fine with my other cats. He and the male are buddies but both my girls are terified of him, possibly because of his size as he is almost twenty pounds and not fat, just big. They spend most of their time hiding from him. He, of course, chases then when they run if they see him. The stress and anxiety caused by being chased is causing issues with my 2 females. I've tried everything to stop the chasing but nothing has worked. It breaks my heart to part with him, but I'm afraid for the well-being of my girls. Chui sits on my lap every night to watch TV and is very affectionate - a real attention hog - and laid back except for that one issue. He'd be perfect as an only cat for someone, especially someone who likes a lap cat to watch TV with them. I don't know about dogs or kids, and other cats is, of course, a "maybe, maybe not". Shots are up to date.