The lock is not necessary to keep the snake in the cage. I get them to keep other people out of my cages.

As long as the room the cage is in stays above 68 F Flexwatt will be enough. I live in Orlando and That's all I use on my cages. The available fluorescent light fixtures will also help boost the air temp inside the cage. I would get at least 1, but preferably 2 (if you are planning on using a divider with the cage you have to get 2 lights)