1. Do repeated interactions with other people seem or feel extremely unsafe to BPDers? (e.g. coworkers, people you have to see routinely, etc.) to the point where you feel a panic or an urge to quit jobs or move to a new town?
Absolutely, positively, painfully, yes. I am pretty "straight" on the outside now so I normally (now) do not "reveal" myself to people easily. If it happens that I get close, than danger is there, I feel I have no boundaries. It is like a dike is collapsing and out of the fortress comes out in waves all the intensity. In the past yes. I have moved countries, houses, dumped jobs, friendships, everything. Now I manage a bit more my impulses but right now it is difficult. I have met somebody that is getting closer and for me is like going from 0 to 100 in less than a second. Fear to scare off the person. Fear that the chaos will break out loose.
2. Is there such a thing as 'mental self-injury' where you have the urge or compulsion to think of terrible things, get a pit in your stomach or a fright (kind of like intrusive thoughts) ... and perhaps feeling strangely more safe or secure afterwards?
no. But maybe this could help me out of the current obsession
3. Do ruminations and anger feelings come in recurring waves? Just when you think they've gone, they surge again?
kind of. Not really anger feelings. But feelings in general have the power to overthrow my mind. Where is my mind?

thoughts always racing. a torture