Don't even think about removing any of your work. You could be arrested for vandalism, theft,or trespass. It's hard to say how this will turn out without a contract. The key to service work is contracting. There's a saying that goes something like "The value of service diminishes rapidly after completion".
Was this a T&M job with the shocking invoice at the end?
Dave
I was thinking the same, hard to say, how this will play out, without a contract.
We just hope he thinks about this, on the future jobs.