OMG I'm so so sorry for little scooter !
Please don't shoot the dog - please don't. That isn't the way to go and your family needs to step up and take measures he never near kids...and other dogs - any animal actually....but it isnt the dogs fault...it's your brothers fault
and I'm very sorry for that.
IF I were in your shoes ....I'd do all I could to get my own place and start fresh -this is a dangerous situation for your daughter.
You have my condolences for your loss. That had to be horrible