I need help

So I moved in with my boyfriend about 4 months ago and everything has been just perfect. The only problem is my boyfriends dog is a really aggressive black lab. So his dog bit me the first time he met me and we found that if we muzzle him and introduce him to people by going for a walk he usually does okay and we can eventually take the muzzle off. We brought my cat over two months ago and their relationship has been pretty decent. He does okay when she’s up high but when she’s on the floor he chases her mercilessly. So we try to keep them separated at all times because he can’t wear a muzzle longer than 15 minutes and I don’t trust that he won’t try and hurt her. We also just got an 8 week old puppy. Eventually the puppy should get bigger than him, but for the moment letting them be together is potentially extremely dangerous. We had them separated by a baby gate and his dog was growling and tried biting our puppy through the gate. He said that his dog was probably playing but I didn’t see a tail wag and his growl didn’t sound like his play growl.

I feel uncomfortable because I don’t know how to tell him that I don’t feel safe with his dog being around my cat or our puppy. I also don’t know if it’s something I should tell him. But his dog is extremely aggressive and recently growled at me for trying to get him to stop eating the puppies food. I’m scared of his dog but it’s his baby and I guess I don’t know what I can do to protect my relationship but also my fur babies.