I am a childminder and feel very at this. The child is obviously very unhappy, and I do feel if you are only minding for the money, you are minding for the wrong reasons - Sorry, but I hate to hear that from childminders, and as a support minder I hear it quite often.
Childminding should not be seen as something you do for pin money, the children should always come first, yes, you need to balance the needs of your family as well, but minded children deserve the very best care you can provide.
I think your son is picking up on your negativity about the child, and as for your husband's attitude, I am shocked.
My DH has an office at home and he knows that some children take time to settle and can cry, but he respects that it is my business and supports me fully.
Harsh words maybe, but it is not a job you should take on lightly, it needs commitment to every child, not just your own. I have had difficult children, some need more support than others, and this child is telling you that.
The little boy needs to move on to somewhere he will feel loved and cherished, to have fun and be valued. For his sake, give notice.