First, Welcome to the Forum!!!
Smoke detector and Carbon Monoxide detectors I'd get at Big Box. Propane detector you'll probably have to get at an RV place if you can't find one online you like.
I'm guessing you have an INverter not a CONverter (they're different). The inverter allows you to run 115v appliances off your batteries; A converter is more like a battery charger.
If your fridge is propane the 3 batteries may be all you need; depending on the solar capacity and how many other appliances you're running off the inverter. Coffeepots and microwaves don't use that much in the grand scheme of things because they're not on for very long.
If you have an installed voltmeter or ammeter learn what it does and how to read it. Probably 1/3 of all the problems with boats are electrical, and it often comes down to batteries. Learning how to monitor them is essential.
She's a tired old barge but she's paid for! http://s71.photobucket.com/alb...p;current=ef324993.pbw