Dozer Construction and Painting

My dad's home was damaged due to Hurricane Harvey. FEMA gave my dad funds to have his home repaired. We hired Dozer Construction and Remodeling to do the job due to a lower bid. (FEMA only gave my dad so much). My experience with him has not gone well. He has not been at my dad's home, nor has he completed the job. It's been months now and he keeps putting us off. He hired someone who smoked pot in my dads home and when I mentioned it, he fired the guy. He's had stray workers sleeping in my dad's home. He won't return any of our calls and won't provide any receipts as to where the funds were spent on materials. I am hurt that a contractor would take advantage of people like this. He is unprofessional and hires drug addicts and anyone else he can find to do the work. None of his workers have been paid and my son is paying them out of his own pocket as well as buying materials out of his own pocket to have my dad's home repaired. I need legal help and advice. Can someone tell me what to do or point me in the right direction to either get my dad's home completed or to bring legal action against this guy?