I have had to remove the Autohelm, 3 times under warranty, and had to tighten the chains. Not a good job.
I could not find any definitive answer to how tight they should be. I did over-tighten once and found the wheel a bit stiff.
Your fan belt movement seems about right. Before putting the cover back on, turn the wheel from lock to lock to ensure you have full movement. If the chain comes off the sprocket, it can be difficult to put back on. If the chain jumps a few sprockets, the adjustment mechanism may prevent the wheel turning to full lock.
I can't remember the product I eventually used, but I originally put some nail polish on the thread to lock the nuts to stop the chain working loose. If the chain comes loose, the loose chain will fall down and jam the bottom sprocket. This has not happened to me but I know of one boat where it did happen and the rudder was locked on full turn.
Craig
"Shirley Valentine"