Joe...thsanks for the clarifications. On your questions:
2. Do you have ANY switches presently on the boat that turn on and off any AC powered devices or even the AC outlests?? If not, and your shore power is wired directly from the master AC switch only to outlets then you will need to install a small AC breaker panel...with at least one switch for your outlets and one for your charger...I would get a breaker panel with at least a couple of more switches than you need now.
3. Should be answered by 2 above. Shore power, main AC breaker, Individual AC breakers on panel, charger is the order. Charger output to the battery switch for NOW.
4. For your plan...the chargers power SOURCE should be the AC breaker panel...and the destination for the charger DC output should be one of your two house batteries rather than the battery switch. You should not get a charger with multiple outlets since you are planning on charging one bank and using an echo charger for the starter battery.