Hi dyspraxia,
I am wondering if you are having complex partial seizures, the reason I say this is because I start seeing colors flash back and forth in my eyes at the beginning of the seizure then I blank out.
Have you had a PET or SPECT scan done? This will show a lot more detail of what is going on in the brain. PTSD can really effect some people really hard with having flashbacks, my grandfather had them from WWII.

The best way to deal with your sister and family is to be open about the problem and explain to them what is going on. I've done this with my family and friends and it has helped them understand me much better.

You Dad needs to speak with your Dr. or see a medical report from your Dr. so he will realize this is all true and he needs to face up to the matter and be supportive.

To stop yourself from running away from home think about other people in this world who have things in life a lot harder than you do. I saw my aunt with MS, and she couldn't walk, along with working with students in school who were in wheelchairs for life do to medical problems. This woke me up and made me realize how lucky I am and that the seizures aren't lasting.

Here's wishing you only the best and May God Bless You,
Sue