The Lynx distributors clean things up considerably and are the way to go. If you have access to a dieless crimp tool then nothing wrong with extending your existing cables using a butt splice although a new unspliced cable is always preferable. Welding cable is better to use than standard...
Same here as I didn’t want to cook my alternator. Your multi plus does have a 4 amp trickle charger for the starter battery. Single positive wire from the charger to a positive post at the starter battery. Fuse this wire at the battery.
Staubli connectors are the best and you should not mix brands. Equally important is to use the proper crimping tool. There was/is a video online used to certify installers using Staubli connectors. You can also buy PV cable with connectors already installed. PV cable comes in different strand...
The green ground wire is a bond wire for the inverted AC. It should be attached to the frame of the Moho somewhere. You may find it attached to the frame along side the bond wire from the gen set and main electrical panel. Hard to see in the picture but where is the second ground?