True. I agree with you.
Walt could have killed them, by not calling off the Nazis, and actually helping in the ambush. The fact that he called it off, and was willing to turn himself in - means that he didn't want to Hank to die. It really wasn't a matter of, he was caught - and there was nothing he could do about it. That's not true. He could. He had access to a hit squad he could call in.
Walt's not stupid; he had to know Hank's death would cost him Skyler and the kids. I don't think he particularly wanted Hank dead, but I do think part of his meltdown post-Hank-death is knowing that he'd almost certainly just lost his whole family.He'd never have called a hit in on Hank because the end result, even if he didn't go to jail, would be worse for him.