I just thought I would chip in. I am not an expert on this topic, I just want to let you know about what I have been told.
If you go after them and you win, chances are your insurance company could come back after you. Why? If you knew about the possible issue and still drove the car while you thought it wasn't road legal this is a breach of insurance conditions and you should not have been driving it.
Now in your case, you are kind of safe from this, because you thought it was repaired, but you being "smart" could put you back into the above category. Just be aware of this because this could mean you loose all the $$ you spent on the car and have to pay for everything (including 3rd party) out of pocket.
Regarding the car company, no one likes being told how to do their job and big corporations seem to be the worst. Remember their customer base in the last few years have been driving Priuses not petrol heads driving sports cars, this makes things harder for the enthusiast.
I don't think the dealers aren't to blame (entirely) in cases like this, even from your story I feel like the dealers were/are trying to be helpful, but you can only do so much because all warranty claims have to be approved by the head office.
Anyway best of luck, sorry if I came off rude or anything, hope you get it sorted
