Hello planejane13: I'm so sorry you have experienced all this trauma.

I must say it is difficult for me to imagine anyone could even survive such repeated onslaughts.

I don't know as I have much in the way of advice or words of wisdom I can offer.
From my perspective, what your T said about setting boundaries is certainly correct. On the other hand, sometimes, in the face of a flood (or perhaps a mudslide?) the best thing to do is to get out of the way!

It may be that in order to finally heal, you are simply going to have to put distance between yourself & all of these people. Otherwise, you risk becoming "re-infected" over-&-over again not unlike someone who is repeatedly re-exposed to another person who has a contagious disease.

I realize this may be difficult given that many of these individuals are family. But sometimes, setting & enforcing personal boundaries is simply not enough.
And then, along with that, perhaps you may want to take a look at whether or not you may be, to some extent, setting yourself up for additional problems (as with the transgender person you mentioned.) It may be that your desire to help others who are struggling is also predisposing you to having additional disturbing experiences... just something to consider...
I send my best wishes your way with the hope that you may at last find your way to lasting peace within...