I get the needing a plan for every eventuality thing, I'm not great with uncertainty either. Given you're stuck with the situation at least for a little while are you able to find a way to accept that it's going to be difficult and that they're going to do things that trigger you etc.
I find that when I anticipate being in a difficult situation and try to fight my reaction it just makes things much worse. I end up in full flight/fight and it takes ages to settle again. If I just accept how hard it's going to be and really work on self soothing it seems to pass more easily. It's different to just giving in, in that you're recognising your boundaries are being pushed but you choose to accept that's how it is for now. Might help take some of the sting out?
I find that when I anticipate being in a difficult situation and try to fight my reaction it just makes things much worse. I end up in full flight/fight and it takes ages to settle again. If I just accept how hard it's going to be and really work on self soothing it seems to pass more easily. It's different to just giving in, in that you're recognising your boundaries are being pushed but you choose to accept that's how it is for now. Might help take some of the sting out?