An M2 is not designed to work with a laptop. It can be jury-rigged to work, but is not the ideal solution, IMHO. I'd look at a Carnetix unit instead.
If you want the laptop to power on/off with the ignition, you need some means of pulling that off. You can crack open the laptop and attach to the power button, use WoL or WoR and other methods depending on hardware.
Do some research to see what will work with your laptop and what will be the best solution for your install.
A fuse needs to go on the +12v line from the battery and it needs to be as close to the battery as possible. Within 12 inches of the battery is ideal.
Have you looked in the FAQ yet?
How about the Wiki?
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