Nitrous plumbing A1A...??..

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These are the installation instructions for the summit window switch. It looks like I would have to take the ground wire that I have just outside the low pressure switch and run it back in to the blue wire? I believe running the ground through the window switch to it's black wire ground?..
My concerns become with the 3 amp capability?? Currently I have a 5 amp fuse feeding the nitrous activation switch. Which has a little green light of unknown amperage and it goes out to the trigger button on the shifter which along that coming out of it going to the full throttle switch is giving a signal to the MSD timing retard which I'm not sure how much amperage that sucks up? Then like said it continues through the full throttle switch to the nitrous relay which itself probably only takes a half amp as far as I know?..
Right now the best I can think of is putting a two and a half amp fuse into the blue wire of the window switch so it would blow if it got any more than 3 amps?..

This is where a hand drawn schematic comes in handy :)