Where is your evidence that he has put lives at risk, where has he skimped to save?
Well - all those photos you've posted that show he has previously employed tradesmen of the dangerously-incompetent-cowboy variety! And the fact that, no disrespect to your abilities, he's asking his tiler to sort out the mess.
It might be a good laugh, but that electrical installation could easily kill somebody. One of your photos shows it nearly has. This guy needs to wake up. You don't have the qualifications/insurance etc to take responsibility for what you're being asked to do.