what im doing about this situation

Hello, we are about 98% done with the job we are working on with an investor who does flipping houses. We're just waiting for his plumber to finish something in the bathroom so we can finish the job. He keeps saying we aren't allowed to go there anymore and gets mad that we won't do extra work for him. The final balance $17,500. And he only gave us $8.650. He still owes us $8,850. I texted him and told him to let us know when the plumber will be there so we can finish and get the final balance. Now, he's saying he doesn't want us to finish the job and doesn't have to pay us anything else. He even said he would process us because he said we agreed to do extra work, but we can't do it. He gave us a lot of difficulties, so we chose not to do any extra work for him. We did not do extra work for him because working for him is complicated. And we have all the proof of him saying this; we have texts, pictures, and more. I told him that we would discount the part of the bathroom and pay the rest if he didn't want us to do the bathroom. But he keeps insisting no, even though we did everything else on the job. This is why we need help because we need this final balance. Thank you.