Don't be sudo gainrooting on a whim: it's asking for trouble. For example, you've now made the config file belong to root, so that the app can't alter it. Sudo gainroot and type:
chown user ~/.accelemymote/main.cfg
and then type exit and don't sudo again unless you know why you are doing it.

The tilde (~) represents your home directory to the shell, so ~/.accelemymote/main.cfg is the full location of the file. It's in your home directory under a hidden subdirectory (begins with '.') called .accelemymote.

You are right though that it doesn't do anything (besides change the value in the config file). Apparently it's not using that option properly yet. Next version...

You can try changing the poll_rate parameter in the file to something lower, but in Doom you are either moving, running, or not moving. I'm not sure there is a "slower". If there is, it will be via analog joystick support which is not implemented yet.