I dont have any medical training in these areas, but i have done enough reading to tell you that the other posts here are correct: face to face contact between her and a trained professional is the only thing that will get any actual results. Said theoretical professional will probably also need feedback and support from yourself and your dad. The fact that any one of those symptoms could be part of any number of diagnoses, and steer you to the wrong treatment isn't even the only problem. The thing about these sorts of things is that mental and physical illnesses can co-exist in any number of combinations, and be caused individually by any number of things. Concisely identifying a list of the most apparent and most alarming symptoms is definitely a good solid start. Save that list for yourself, whether you choose to show it to your dad or not.

That said, I feel i must also advise against the idea of taking tests and trying to guess at how you think she would answer the questions. In my own experience, i find that the shift from one frame of mind to another can drastically change my responses to some simple and insignificant questions. (What shirt do i want to wear today?) And I am using a small-scale example on purpose, given that your stepmom seems to change mental states a great deal more drastically.

I really do think it is great that you care enough about her to post here and ask for help. I wish i had a better answer for you, one that would steer you closer to finding the problem. I wish we didnt all have to give you a non-answer of an answer, but, it happens that in this case that is the nature of the problem.

Best of luck to you really though.