"= 3. Should I also protect my shore power system? - I leave the boat
plugged
in with the refriderator and battery charger running.


Leave your fridge running on AC power. Turn off all DC components while away
from the boat by turning off all DC circuit breakers on the electrical panel
and also the main battery switches (make sure the bilge pumps are wired
direct to the batteries). Definitely want to leave them powered while away,
but not much reason to have any other 12V device powered up while away. If
the marina has a power outage while you're away, the fridge will probably
hold it's temp just fine until the power returns.

With no DC load on the batteries, there's no reason to leave the charger
turned on. I used to leave my charger turned on years ago. Batteries and
zincs suffered greatly because of the practice. Leaving the charger off
while away has had a huge effect on extending battery and zinc life. Well
maintained batteries will hold their charge just fine while you are away
with no load on them. An even better way to maintain charge while away is
to convert to good quality AGM style batteries. Negligible self-discharge
rate on those, and they last a very long time. Zero maintenance, to boot.