I don't know what he is tightening up with the oil pan off if he didn't replace mains or rod bearings. It sounds like you lost a rod (if I'm reading this right) If he didn't overhaul the bottom end I don't know why he should stand behind it. But if he retightened the rod and main bearing caps, then you have a sticky situation. It could have broken a rod bearing cap stud by overtightening it when he "retorqued" them. Maybe not when he tightened them, but when the engine was started and got to operating temp again.
I'd ask him when the last time his torque arm was recalibrated and how it was done. I'd like to know so I don't have to run to get mine every time I want to torque something.
If his defense is that he has a "micrometer eye" and a "torque wrench arm"....then I'd say he is full of $h!t and hope he admits it in court. Make sure you bring your own professional witness.
Anyone can take an engine apart and most can get it back together. Some of them will run OK.
A real mechanic has the correct tools and finds the right person who does to do specialty work. He knows not only how it goes together, but how and why it works. He also stand behind his work.
Your trouble is that he "didn't" rebuild the bottom end. THe thing you have going for you is that he worked on the bottom end with his torque arm (if I read this right).
