i have dealt with this too. the funny part is the work isn’t bad. it is the people. people tend to ruin the work. it is funny how this experience will change your whole concept of how you approach cars/customers to protect yourself. don’t be afraid to turn down jobs. it is hard to do but sometimes it is not worth it to take the job.
i would call the bluff. some people think threatening attorneys will get things done. all it does is piss the owner of the shop off. sounds like a shit for brains kid that thinks he can get somethin for nothing.
you know even after the head is repaired and car is back together their is pre existing problems that he is gonna say that weren’t there before you touched it.