Problems with contractor

[Clenvic Cayme]

So me and my brother recently got our first deal in November. We interviewed and got quotes from several contractors, and one of them seemed to be by far the most knowledgeable and reasonably affordable. He was also recommended by a seasoned real estate investor that we knew so we went with him. At first everything went very well, he was on top of his game and was doing work extremely fast and in high quality. The problem is that around December he had health issues. He got pneumonia and has developed adult onset asthma. I know this may sound like BS, but my family is full of nurses and they can tell that he is genuinely sick. We tried to be understanding with him and give him more time but it seems like he's just not healthy enough to finish the project. It's been 4 months and the initial time estimate was 2 months. We are getting weary and want to put the house on the market. 

We've now told him that if we can't see significant progress in the next week we're moving on to another contractor. The issue is we've already paid him $30,000 out of the $41,000 initially quoted for us. The issue is I'm not sure if he's going to give us all the material like he promised, since he still hasn't been paid $11,000, he could just say the rest of the material was in that next payment. 

We really want to stay with him since he's a good guy, but every time we talk to him he says it'll be finished in a week or two and then we check up on the house and there's barely any progress. 

What should we do???