I have one more thought. I might be sticking my foot in my mouth, but I will take a try at this and hope I don't offend.
Thanks for all the responses so far, keep them coming!
A handful of people have responded, and no one here has even slightly suggested there are any reasons to stay. But you ask for more input... Which is totally ok and good! (please hear me on that) - but it does raise a question for me.
I think it is great you are seeking outside input - but this is one circumstance where I sort of am wondering a little bit if more outside input and opinions about if you should stay or leave is what you really need?
Let me see if I can explain...
I myself was once involved in an unhealthy organization - one that I initially promoted. It was very painful when the red flags came, and it took awhile for me to finally pull away. So I can understand a little of what you might be feeling right now and the pull to stay and not walk away yet, despite all the problems. Its hard to let go of what we have really invested a lot into, even when there are good reasons to leave. We all need people to help point out things for us at times - everyone has blind spots. (I think I have about a million myself.) You are clearly weighing this out and thinking it through, and I think that is good!
As you know, this is a PTSD forum, and many people here have survived terrible relationships and environments. Folks here do generally have sharp radars for problems. I think it is a great idea for you to ask for input here. Even more input...
I also don't think you will find anyone here who is going to tell you it's a good idea to stay in an environment where you feel pressure to do things you don't want to do and an environment that sounds like it is very psychologically unhealthy. People here have been deeply hurt by varying degrees of those kinds of environments. A forum for sorority organizations might have some folks who can tell you how great sororities are, and that it is worth these problems, but I don't think you will find many folks here of that opinion. Maybe you will, maybe I am wrong, and some people here think you should stay... But I am not sure even you expect someone to say, "oh yeah, this sounds like s great place to be involved and is good environment for someone healing from trauma and wrestling with PTSD symptoms." You yourself have clearly recognized some serious problems and you have listed them out yourself very well.
You have seen many red flags from early on in your involvement (or the initiation of the alpha class, which I take to be early on in your involvement) and you have seen these red flags for quite some time, and yet still you have stayed.
You have sacrificed much and still sacrifice much, and you seem to get very little in return from these relationships... and yet still you have stayed.
You have taken steps to disengage, and turn over your responsibilities, and in some cases those responsibilities are being painfully taken from you, and yet still you have stayed.
So all this makes me want to ask you what someone once asked me... When will you be ready to listen to and trust yourself? What will it take before you take responsibility for your own choices and role in being involved or not in this environment, and who you let be in your life or not?
Because in the end, it's not your mom's opinion, or your boyfriend's opinion, or the sorority girls' opinions, or the faculty members' opinions, or our opinions that really matter the most.
It is your opinion that matters the most.
Whether you stay or leave, I hope it's your voice you learn to listen to over all the others. Once you are ready to do that, I think you will know what you need to do very clearly. (Which may or may not include leaving or staying.) Learning to listen to and trust ourselves is also an important step in healing from PTSD and trauma for many people. It is for me, maybe it is for you too.