[folivier]

Eric, you could possibly squeeze three 100 amp BBs in the space of one 8D but they would probably be sitting on top of the angle iron rack. But since these do not require any maintenance you could remove the rack and set the BBs on a shelf (they only weigh 33# each). So each 8D has ~ 250 amps (but only 50% are usable) so you could conceivably almost double your capacity. According to BB it is ok to draw their batteries down to 0%. I don't plan to go below 20% SOC on mine.
You'd have to measure carefully to fit 3 BBs in the space of one 8D and the heavy cables would be a tight fit. Or you could attach each battery to a heavy bus bar.
But the first thing to do is an energy audit to see how many amp hours you actually need. The big refrigerator would require at least 1 BB just to run it. Other things like the microwave, 120Vac water pump, etc. need to be added up over a 24 hour period. Then how will you recharge them? Generator? Solar? Engine alternator?