Let me get this right, where you are at, you have to have a minimum of 2 acres even if you purchase an EPA approved unit. I would not suggest putting any wood boiler in a barn with wood floors or walls period as there is always the chance of fire from stray coals or flashback when the feed door is opened. If you were to create a fireproof room to house the unit and connect to the chimney, then I would certainly suggest a gasser as it will significantly reduce the creosote and ash going into the chimney. In a perfect world you could put an EPA certified stove beside the barn, no extra stack, 20 feet from the barn, and use the barn for wood storage. If you were to put an indoor(pressurized) boiler in the garage use lots of caution when plumbing to create a non powered dump zone directly above the unit to dump heat in case of a power outage when you are not home as the unit may overheat and pop the safety relief valves causing a mess, in other words, I think you have to think about this one before jumping into something that may cost you more than the benefits of burning wood. Start by contacting your code enforcement officer again and specify the codes on an EPA approved stove as setbacks on these are dramatically reduced in most areas.