Jenn Jubie, I think it's fantastic that amidst your already busy and stressful life, you seem to be very dedicated to this child and his needs. I think it's terrific that you can separate his behaviour from his personality and it sounds to me that through your personal experience that you realize that in the bigger picture this may not be something he is able to control. Everyone needs a support system who will be their for them regardless of who they are. Family, friends, neighbours, caregivers of all types are what any child needs, let alone one with some special needs.

That being said, I don't think under these circumstances it's a good idea to keep this child on. While you are busy taking care of everybody else, it will be at the expense of yourself, which isn't good for you, or anyone. I think in this case, IMHO you should absolutely give notice to this family. You can not give notice to your MIL lol, and caring for the elderly is draining at best, let alone a family member. It doesn't mean you don't care about this child in the least, but that you have an obligation to your family, that you obviously can't get out of, and you need to reduce your stress load in order to maintain a somewhat healthy mentality and lifestyle for yourself. You say you are dealing with stress ok right now, which is a good thing, but this kind of child, if he is special needs, is going to get more needy as time goes on, as is your MIL by the sound of things.

Do not feel guilty. This child can be well cared for by someone else, while you can use all that energy to take care of your own family and most of all yourself. Good Luck and keep us posted. Sending you hugs