Is my dog worth keeping now?

We have a yellow lab who is 9 yrs old. He is a very funloving trusting and kind dog but a little monster sometimes. He acts like he is a puppy still and to this day we have still not been able to train him to not bark when ppl ring the doorbell and also to back off when ppl come over. I have a 2 year old lil girl and Im pregnant with another. Last Sunday we went to see Harry Potter and had a babysitter for Cordy. The woman told me she will deal with the dog if need be since i offered to put him in his crate since he was a lil over the top excited. When we came back the dog was cowering. She told me the dog was stepping out line and she "dealt with it" and gave him a good whack. I didnt question it at first because of all the commotion of being back home and a 2 year old is ecstatic to see me. I asked the sitter about it before she left and she said she took her fist and plowed him a good one. I dont know where, I dont know how many times. My lil girl told me also that the sitter hit our dog and our dog cried, when I ask her if she hit him lots she says yes but im not entirely sure she understands. Since then the dog has been agressive towards me and my 2 yr old. He isnt like this at all. If we walk by him he growls. On Tuesday the dog snapped at my wrist when i told him to go to his crate after letting him back inside and he snarled at my 2 year old baring his teeth. I dont want a dangerous dog in my house and I dont know if there is anything I can do to get him back to the way he was. I am pissed this woman did this and there is nothing I can do about it. Reporting her without proof is a waste of time. I dont want her back as a sitter or at all for that fact but now im stuck with this dog that sits in his crate all day refusing to come out who growls when we are a few feet from him. He is fine with my hubby and doesnt growl at him so hubby thought maybe the dog is afraid of females.... Should I try and get this dog help or is it just safer to find a friend to take him or list him in the newspaper. I honestly dont have the time now to retrain the dog and I have no clue what I am doing either.