Need to vent/advice

Me and my fiancé live together and long story short kinda his parents had 2 dogs. His dad passed in January of this year it's been hard we'd been trying for 4 years and found out in March were expecting our first. 
So his mom moved out and ended up taking one of the dogs leaving the other here. 
He's an old dog but mean.
Couple days ago he tried to bite me.
I don't want him here around our baby. But today he basically told me he would take the dog and leave. 
I'm very hurt and angry, sad. Don't know what to do. We've been together almost 7 years. It pisses me off he'd rather have the dog than his daughter. 
What should I do at this point? I'm so lost and confused and can't really talk to his mom because our relationship hasn't always been good.