Hi there and Welcome to YT! i am very sorry that your dealing with so much right now, and your child being so ill. i hope the best for you and your little boy.
I have A 10 month old Yorkie puppy, and she is the most sweetest little dog in the world. SHe loves people, rarely barks, and just wants to be around us at all times. All dogs have different temperments, just like people.
I would definately keep looking for a better , more nicer Yorkie . The one you looked at was a mix that has Guard dog characteristics. I'd stay clear away from that one.
Getting A Yorkie a yr. or older does look like it will work for your family. Look at the temperment of the dog, because I feel like this is very important. your going to want to try and find a good match.