I have friends and ex-colleagues who are in the same situation. They're very worried too. I also have a good friend who lives in Austria with her British husband, one child who was born in the UK and another born in Austria. They're all looking into having dual nationality, but it's a worry and no doubt will be expensive.
It's all very well saying the UK could set a precedent, but this is politics - people don't always behave like 'British gentlemen'. I don't like the situation any more than you do and I still wish I could wake up and find the whole thing has been a bad nightmare, but that's the way it is.
In the end, it probably will be OK. I can't see that the civil service has the staff to process four million applications for citizenship, work visas, etc and to deport all those who don't qualify. I doubt if Spain relishes the idea of deporting two million British pensioners either. However, it's all agreed and signed, I don't think anybody should be trusted.
Hammond is right about yesterday's vote being non-binding according to parliamentary procedure.