BFs mother trying to break us up, what can I do?

I've been living with my boyfriend for a few months now. We started in basically our own place, but his brother kicked us out, with the grand help of his mother.

I moved home, got kicked out within a week and ended up moving in with my boyfriend at his mother's. She gave him permission for me to live here, making the comment of "I don't hate her" which I found a bit of an odd thing to say.

On saturday night his mother's dog bit me for the second time. Not. My. Fault. BF said it was the worst she'd bitten anyone before (and yes she's bitten a lot of people) I'm having trouble typing this because two of my fingers are so ******* numb. She bit me several times on both sides of my wrist and I was literally dripping pools of blood into the sink at the time.

She's shown no remorse at all. Hasn't asked me how it is, hasn't apologised for her ******* dog almost slicing her mangy teeth into my arteries and doesn't seem to give a **** in general.

Dr told me I could report the dog to the police, and man would I love to put a bullet in it's brain myself.

Only thing is, it's my boyfriend's mother and I could **** our relationship over majorly if I report his mother.

If it had been any of his other brother's girlfriends she would have made so much of a fuss, apologised and generally been embarrassed that her dog had perhaps permanently scarred them or damaged the nerves in their fingertips forever. My hands are tiny and I was really terrified (since the dog didn't let go until my BF stood up) that she was going to sever my fingers or even cut right into my wrist and I was going to see blood pumping out of a gaping wound.

I've had to take two days off work so far because I literally can't do anything, it hurts my wrist to the point of tears just lifting something up. It makes me feel sick and light-headed when I brush anything against my numb fingertips, but she still doesn't give a ****.

Yesterday my boyfriend was poorly, had an upset tummy, got up and told his mum he was going to take the day off work (they work in same place) and she immediately said "Is SHE going into work?" and then called him a liar when she got home. In the morning, when my BF came back into the bedroom after his mother asking if I was taking the day off too, he lay down facing away from me and said "I don't get why my mum thinks you're the devil..." He was really upset, and I just tried to make him smile. He went on to comment that she always started calling me a bitch and getting angry when I left a plate on the side, and complains about having to do my washing (though she shrinks everything and the washing powder leaves our clothes sticky and horrible smelling, so I said I'D do ALL both of our washing) etc etc, but with my BFs brother, she lets him get away with everything, his GF doesn't ever talk (and their mother has complained about the fact that I don't really talk much to anyone (why the **** would I want to talk to her, my BF is the only decent person in the house)) the GF leaves plates and pans of mouldy food lying around, leaves all her washing here, but doesn't even live here and his mother hasn't complained a word about her. It's all "Oh, Sammy's so shy"

Anyway, it's getting me and my BF down, and I'm sick of it. She couldn't give a ****, and it's hurting my boyfriend. I don't want to get into an argument with her, because my boyfriend would be upset. She's basically slagging me off to HIM, again, and it's unfair. He shouldn't have to choose between me and his mum, but she seems to think she's so much better than everyone that she's selfish enough to just do whatever the **** she wants.

I don't know what to do. We're planning on getting our own place in may, but that's 3 months away and despite all efforts this vile woman seems to just hate me.
I was just shocked that my boyfriend, with no prompting, would pick up on this behaviour and her attitude towards me.
My mother has offered for us to live back at home, but we don't get on when we live together, and my boyfriend doesn't like my house. It's cold, damp and has no heating. I don't want to move back home, but I feel if we stay here his horrible mother is going to break us up.

I don't know what to do about the dog either, I really just want to let it go and get run over or get someone to come out and terminate it, but the bf would get upset about that too. I just can't believe his mother could give so little of a **** when I could quite easily be scarred for life or have permanent nerve damage in my fingers. She came into the living room last night and was being overly nice to the dog, just because I was there.
It's usually "******* get out Sybil" but last night it was "Come on sweetie, out. *haha* that's not out, that's lying down, come on!"

She's just a devious nasty piece of work and there's very little I can do about it.