All the other weirdness aside, I think you'll have a difficult time should this go to court, convincing a judge that your friend should not keep guardianship *because you want a different third party to have it*. I mean, you're not saying "It was temporary until we completed much needed repairs, and now friend refuses to return our child".
Instead, you're saying that you and your husband could not provide adequate care or supervision for your 4 year old, and so you allowed the child to go live with your friend. And now, you don't want the child back - you want to have yet another 3rd person provide care and supervision for your child while you continue to "see the child everyday", but not actually parent.
That's not judgment. That's exactly what an impartial person is going to hear when you describe what is happening in your household. You're working literally all the time. Your husband is a SAHP, and yet the house is falling in on itself, and the child is out of control. He can't drive, isn't employed, and the child is extremely violent and disruptive when in his care. All of that points to some level of neglect, especially when added to the condition of the home.
I'm from Missouri. I know plenty of people who were simply too poor or too incompetent at home maintenance and repair to adequately care for an aging home - especially an aging mobile home. There are PLENTY of services in MO to help one bring their home up to code - and most of those are accessed through DSS. You can call them yourself and ask about these services.
But in my opinion, that's a completely separate issue from the issue of you sending your child to live with various other people for an indeterminate amount of time while you're unable to provide care.