Alex, What a rough road you travel. I'm glad you are searching for the answers! My experience with sleep paralysis over the past 30 years has been they happen when I am extremely stressed. I find that If I take a good B vitamin daily and up the dose to 2 daily when life is hard, that I don't have them. I also take a good bit of potassium for restless legs. My brand of choice is Nature's Way Mega Stress because it also gives me my magnesium. Magnesium is excellent to help you relax. I did my research of dosages and possible side effects and usually I will go to the highest amount I can take in Bs', Potassium and Magnesium.
Your description of what happens does sound like sleep paraylis to me but I am not a Doctor. My experiences were being fully awake but paralyzed. Not a dream. I found the only control I had was over my breathing. I would start taking deep breaths until I could wake my body up. If I fought against it, I would get horrible noises in my head. I haven't had an episode in the last 8 years once I made the connection between the B vitamins and the issues. Hope that helps and God Bless!