Thanks for the extra information.
From what you describe, it does not sound as though the problem is a stroke - normally if there has been a problem with the brain such a stroke then it affects the eyes, mobility etc. This sounds like something more local to the mouth/side of the head.
Without seeing your dog it is difficult to say what is going on - could he have banged his head, been bitten by another dog or chewed up something that has caused trauma to his mouth/head? The salivation probably reflects pain and the inability to close the mouth, and whether the ear is sore or there is nerve damage there it is difficult to tell. He really needs a thorough exam of this area, possibly under a sedation or anaesthetic so that everything can be seen more easily and the jaw manipulated without causing him any discomfort.
I agree that he needs to eat soon, and if he can't keep food in his mouth then he probably can't drink properly either, so he does need veterinary attention soon. Rather than the children being concerned about a vet wanting to put him to sleep, I would say that the sooner he is examined and treated, the better his chances of getting better by a very long way. Whatever is going on in there needs looking at.
I'm sorry that I can't tell you exactly what is going on, this does sound pretty unusual, but given the severity of the signs, I don't think it is likely to resolve on its own.