It's okay to cry. Sometimes that helps me feel a little better. And you know you can always come here to vent.
I'm sorry this is so stressful on you, but you will get through it. I think it's great that he gets to stay at home for as long as possible. A lot of children wouldn't want to deal with the "hassle".
I always think of the crap my parents had to go through with raising three kids. And I figure the least we could do for them when they get older is to care for them as they did for us. And that's exactly what you are doing.
Just think about the times you and/or your siblings probably stressed your parents out. They pulled through it and so will you.
So just go have a good cry and snuggle with the kitties.