I completely agree that you should try to communicate openly whenever possible, but let's not pretend like it's a level playing field. Of course, if the situation is so bad you can't talk openly with your boss, I'm not sure how much you're really losing by being fired (assuming you are able to find employment elsewhere, as is often the case for engineers today).
Sometimes the only way to change things is to incept the idea.
I choose not to work in such places anymore. Obviously, not everyone can do that.
My experience has shown me that it can take years to find the seams that you need to tug on to expose deep-seated work culture problems.
There are other more specific questions you can ask, but they tend to vary enough I wouldn't offer them as general advice.
I have asked interviewers the opposite: what aspects of the team or company need improvement and what steps are being taken to address them? Of course they will sugarcoat their answer, but you can still glean some insight into the company culture for addressing problems.
In my experience most people don't really like their jobs and are just in it for the paycheck (there's nothing wrong with that, bit if you're talented enough to be picky you should be).
Your boss is more responsible at everything you should also do - communicating, noticing issues, noticing morale issues, being able to understand an issue beyond half-sentences, raising issues with management, trying to fix the issues, etc.
So I say, damn it. If the boss doesn't understand that I'm making my last warning before going over his head, bad luck for him.
Maybe I wasn't clear enough but if I wasn't clear enough, bad luck for him. Should have noticed it anyway, he/she is being payed to do so.