OP,
I am saying this kindly, and don't wish to be harsh, but I think youbso badly need to reset.
Whilst I agree completely the guest is a complete user, you really need to take a hard look at yourself as a mother.
You are putting yourself so far ahead of your child and his needs, whilst you excuse yourself with this so convenient people pleaser label.
Your child is going through an assessment period, desperately needs routine and your limited time and focus, and instead of doing what is best for your child, your house and time is given as a priority to a family user.
Honestly, I find that extraordinary.
It really shouldn't be so hard for you to do the right thing for your child, but you are choosing not to, because that seems the easiest option for you.
That is really wrong of you.
Your child needs your attention and a guest free house.
I genuinely don't get how anyone would put a user ahead of her own child.
So what if your husband presses the nuclear button, thats on him if he chooses to do that.
Why are how YOU feel, and the feelings of this user guest, so much more important than a little boy who is struggling and being so badly let down?
It really is a no brainer to put your child first.
Very sad that you don't see that.