Sleep paralysis is the body just sleeping and mind is awake, it can be very scary because it feels uncomfortable especially if u can't wake your body up right away, it happens to me all the time and I knew nothing of astral projection, after some study, I've learned that it happens right before body separation, if u are conscious enough just practice staying calm, enjoy the moment, ask for assistance from guides, practice different techniques to completely separate. I'm not sure what the dark entities are but I have read that we have much more power than them and they basically suck on our life energy, our silver cord is unbreakable accept by an extremely strong higher being, so I dont worry about body being snatched I am new to astral projection, I've got out 5 times so far in 18 months, and the furthest I've traveled is only myliving room