If you love your pets and if you want children at some point, you won't just be walking away from this arsehole for your sake, you'll be doing it for your pets and future children too.
It doesn't matter he's sorry, it doesn't matter he's gutted, he has hit an ex before and he's been the tiniest step away from doing it to you too.
You were scared for yourself.
You were scared for your pets.
Choosing a future with a man who has proven himself to be totally unworthy would be absolute fucking madness.
This is real life now, not a story where you can fix someone broken.
At some point if you stay together, you will anger him and he will hurt you. He will punch / slap / spit / kick and you won't be able to defend yourself physically because he's so much bigger.
He will threaten to hurt your pets and your children and you will feel obliged to stay because that terrifies you.
He will break you down until there's nothing of the real you left and if he fancies it, he'll cheat on you because to him women are things he wants to 'keep' not whole people he respects and cares for.
You've been handed an opportunity on a golden platter to remove this man from your life and your home and if you don't take it you will regret it for the rest of your life.
Be wise, he's a common garden variety abuser. Nothing special, not someone who deserves your help and support, he's a wanker who does this because he can get away with it.
Don't be a statistic and for the love of god if you want kids in future think about the choice you're making now even harder.