Your story is a school case, unfortunately. The law is never in your favor as a single man or small shop. It's too expensive to go to court, then determining w

Your story is a school case, unfortunately. The law is never in your favor as a single man or small shop. It's too expensive to go to court, then determining what should have been done or not done as per the contract is a lengthy and uncertain proceeding. Clients who wanna pay per project basically want to move the risk over to you. They should pay a premium. Write a solid contract and increase the fees/duration. Most should give up when you start increasing the quote just to establish the contract, it's easier to start a POC and see what could be achieved.