HH, I just noticed something else you mentioned... . that this negativity is focused on not just how terrible everything in the world is, but you personally.
This is tougher to handle--you are much more likely to take it personally and get triggered. I found that I could sometimes stay validating for a little while, but if it continued, I would lose it.
I have accepted that the best thing I can do at a time like that is just disengage from the conversation, no matter what is being said/yelled/accused at me--I know the point where nothing I say could possibly make it better, and I know the point where if I say anything, it will be destructive, not constructive. Be ready to just leave an awful interaction before you make it worse!
I personally set a boundary that any time she started telling me what I was feeling, I was not going to participate in that conversation. (I was personally triggered by this sort of projection... . I sometimes screamed something like "STOP TELLING ME WHAT I'M !#@$!@# THINKING"... . I don't recommend making the point that way but it was occasionally the best I could do

)
Another part of that boundary was that I wouldn't argue with her about doing (or not doing) abstract things. I was open to requests to change specific behavior, but it had to be something concrete.
"Buy me a 2014 Lexus" is concrete, and you will both know whether you did it or not at the end of the day.
":)on't be cheap" is vague, and you can very easily have reasonable, honest, different opinions about whether something you did today was or wasn't being cheap.
A pwBPD can very easily change the 'rules' of any argument to make sure you lose, and often will. Don't play that game. You don't need to justify why, just refuse to participate in these no-win situations. She won't fight fair most of the time... . make your own rules of engagement to keep out of those fights.
Aside: If her spending is reckless (+$30k debt in one year sounds reckless), and if you bring in most of the money in the household (I think you do), you are in a position to enforce financial boundaries with her, to protect your financial health. The actions required for this are within your own realm of control.
In your case, I'd get verbal abuse boundary enforcement strong and well practiced before working on financial boundaries--because enforcing financial ones are very likely to trigger verbal abuse immediately! (Or perhaps I should say WW3?)