I agree with prsona. As for the level of danger, I wouldnt say its too dangerous although if youre worried then it might be good to wear some protective form of jewelry, by enchanting it someway. This will help you not bump into any unwanted spirits
Yes it is possible although it is, extremely rare. Astral Projection can be dangerous, it depends. Entities can attack you, you can get cursed, haunted, or even possessed although these things happen extremely rarely and usually spirits protect you as well...
I don't think you can get stuck when you are astral projecting. And if you can you can probably always get out of it at some point.
I also think that you can not get harmed. The harm that can occur is physical harm. The harm that can occur to your body (the body on the physical plane) when you are not 'inhabiting' it. Things like getting burned because a light falls on you or when someone beats you.
If for instance you are attacked on the astral plane, it might feel like you are harmed when you are back on the physical plane. But you are not, it is just your mind making that up.