Here's what I do...
My husband snores and sleeps very heavily so between those two things, unfortunately I don't have him in the bed. He is usually on the couch or on a twin mattress across the room.
I guess it would be safer for the baby to fall off the bed than to get trapped, because falling usually isn't fatal... they usually just get a bump and cry. But you surely don't want that happening anyway! I have a king size bed and there's so much room that I put her on one side and I take the other. When she wakes up to eat, I always feed her on the side that my boob is on ...like if it's the left boob I'll be on my left side and she'll be on her right side facing me. I wait until she's done, put a little something (like a shirt) in front of her hips so she can't roll onto her stomach, and then I kind of back up so I'm not very close to her, and I go to sleep again. When she wakes up again, I reposition us on the bed so that we are in the right place to feed on the right boob - so usually I will pick her up and rotate her 180 so we are in the same spots, but our heads are now facing the opposite direction... am I explaining that in a way that's easy to understand? It's hard to explain! Anyways then I'm on my right and she's on her left facing me, and I feed her and then back up and go back to sleep when she's done.
I don't fall asleep easily and almost all of the time I wait for her to finish. In case I get dozy or sleep while she does, I just make sure to arrange myself so that if I let go of my boob or relax everything, then we will both be staying in the same place and she has plenty of room to breathe.
About a rail/wall, I usually put her between me and the wall - however there's like 2 ft between the wall and her and like 2 more ft between her and me.
For naps, my baby doesn't nap. Hehe well I guess I'm exaggerating... she just takes catnaps under only perfect conditions... usually I have to hold her the whole time, and sometimes on rare occasion I can put her down in my bed and she'll stay asleep. As for the morning, for the first few months I got up before her and she kept sleeping. But now she wakes me up before I'm ready and then we all get up :)
With my first, second and third babies, I was so nervous about breathing that I actually only would sleep if she was sleeping in the crook of my arm, facing up, so basically I held her all night! hehe
Hope this helps to answer your questions :) :)