Well... I think you need to take care of yourself. You need to get to the point where you are not constantly stressing out. I don't know how to get there with out rehoming Nala and Koa, but I really hope there is a way. For Nala, I don't know what you can do, other then what all other pp's have suggested, if you don't think you can handle it, then try and find a home for her. Soon, before she gets worse, its a tough decision, but its one that needs to be made. As for Koa, he has grown up a whole bunch, but thats why training as a puppy is so important. I've seen a small lady handle a friggin monster dog, and she don't back down (Lisa/Rosco). Its to late to even bother bringing that up. But I really hope you can figure out something. Its not fair to you, the dogs, or your son for you to be stressed.