Re: bed rails or suggestions?
You may want to just put that mattress on the floor. Honestly, if he can wiggle that far, he'll probably be able to wiggle around a bedrail (they only cover so much area!). Another option is to pile some pillows around him (or have daddy do it when he leaves in the am) and hope that if he wakes and is wiggling around that he will wake you before he gets away!
I've had babies fall off my bed more times than I'd like to admit. We always find ways to remedy it though. My dd tends to sneak off the bed when I'm changing her and walk off for a second to grab a wipe or daiper or something..