Lighting and Door Problems

[enlive]

Not so much problems as queries really, but when I am making a boxLight entity for my first room so the player can get all of the objects I seem to have 3 choices, either have the light so that it has this wall dark like this:
http://img101.imageshack.us/img101/4687/95854687.jpg
Have it overlapping the wall texture and causing them to flicker, or have the opposite wall being light for no reason. Just wondering, but how would I make the room light without overlapping into the next wall?
And my second question is how do I make locked doors? Thanks.