Do you think my dog has canine dementia? If so what can be done?

My mom's Boston Terrier is 14 years old and lately is becoming dangerous to be around. He will be fine one moment you can be petting him then suddenly he is lunging for you face or arm and biting you. He sent my nephew to the emergency room after he was petting him and he was fine and enjoying the attention then suddenly leaped up and latched on to his face. My nephew got him off and was bleeding and the dog was still snarling and attacking the air in front of him. He has attacked me as well if first started when he would come across me at night if i went to the bathroom despite talking to him he would go for my legs until i flipped on a light and my mom called him then act like nothing happened. He has attacked my sister on 3 occasions and me once as well while petting him. He also will suddenly start barking at nothing and attacking air. He wanders the house a lot and i catch him staring off into space sometimes at least until i move and he notices me. I am honestly getting scared of even touching this dog that i helped raise since he was a puppy. He is just becoming unstable and the only reason someone hasn't gotten seriously hurt is because he is a small breed dog. I know my mom won't even consider getting rid of him and that isn't an option anyway as we really do love the dog. I can't punish him for something he doesn't even seem aware he is doing either. Do you think this sounds like Canine Dementia and if so what can we do? Not petting him or giving him attention anymore would be cruel and seem like we are punishing him for something he might not be able to help. Still it's not good that when he jumps up in my lap i tense up and start petting him while trying to coax him away from me a bit as i am scared he will snap and go for my face and throat. Or if he jumps up on the bed and leans against me wanting attention i tense and shift so that i can jump away at the slightest thought that he is going to attack. My sister isn't so understanding he we attacks her she slaps him upside the head and yells at him until he runs outside then locks him out there for several hours. I just don't know what to do or what can be done that won't end up with him dead or us living in trepidation. Giving him away is not an option either as my mom won't go for it and i don't think anyone would take an unstable dog like this and it also would kill him he has been with us since he was 5 weeks old and just pines and wanders aimlessly around the house when my mom has to leave on a trip. And yes he has all his shots and is otherwise healthy and disturbingly spry for his age according to one vet besides a minor ear infection that is being treated right now.