My Husband Is Making Me Get Rid Of Our Dog

So I had decided to get a dog to add to our family. I went on Craigslist and found the perfect little pit. The lady said he was about 2 and they were moving. They didn't give me much information, and my husband said we should get more information first. The dog honestly looked really sad and I decided to get him against my husbands wishes. He wasn't happy but allowed me to keep him. It took a while to get him used to us but he got a very protective bond with me. I named him Billy. I had tried training him, and it was going well, however he was still super protective over me. He growled at my husband for just being near me. He bit him at one point for just giving me a hug, however he let that go and said he will need to get him a trainer. Well today my 2 year old was tapping me while I was cooking and I said "Go sit down bubba". Everything happened so fast. Billy lunged and had my son by his arm. My husband kicked him until he let go and we had to race to the hospital. My son was bleeding a lot. My son is okay, but my husband said "The dog is out. I want him gone by Saturday." I never felt so scared for my son. I love Billy and he is family, but he really hurt my son. I know I can't keep him anymore. My husband wanted to take him to a pound... But he said we need to re-home him by Saturday