What you’re taking as push back from others is physics and why your ideas will not work, are not efficient and unnecessary. The videos are not relevant to what you need.
A boiler produces too much heat for the space being heated, and your outdoor temperatures. Setting it outside would have to be large enough to not require tending every couple hours, necessitating you to go outside constantly. The firebox would need to be tiny to heat such a small area. A boiler large enough to burn longer without running outside will heat far more hot water than you need. It will be dumping the hot water you are wasting time and fuel to heat on the ground. If outdoor temperatures go below freezing, a glycol mix is needed which would need replacing after dumping the hot fluid before pressure build up. Boilers have to have a temperature and pressure relief valve to release the pressure before exploding. Boilers in homes have many zones with pumps directing the hot water where needed. When no heat is required, it must be circulated to a garage, or other area to prevent the relief valve from opening, dumping boiling water and refilling with cold. A waste of fuel. A boiler the size of a bread box is what you need, filled every hour or so. Not happening.
A furnace needs to be inside the structure. A mobile home furnace heats indoor air, pushes it through ducts, and cooled air is returned to be reheated. You can’t push hot air into a sealed box without taking out as much air as pushing in. It will pressurize the box, pushing the hot air out where it can. Not much hot air will enter the box when very little is leaking out. A waste of fuel outside, with challenges to insulate the furnace and ducts outside, insulating both a hot air supply, and return air. This is why hot water is used outside moving heat inside. You would need to cut much more wall out for ductwork compared to a 12 inch opening to vent a stove.
You need something like 30,000 btu to heat, and maybe 10 or 15,000 btu to maintain. This is just within wood heating range for a small stove radiating into the structure. A water coil on the back of stove can heat water in a tank like the plate heat exchanger video. Set up correctly it can circulate without the need for a pump, but a circulation pump helps drastically.
Stoves in mobile homes must be mobile home certified for reasons other than being legal. They use outside air, (the smaller area you are heating depletes breathing oxygen levels - the stove is using indoor air, exhausting it outside) and have closer clearances to save space. Certified stoves use convection to heat the air, instead of radiation that sets things around it on fire. You don’t have that kind of space. A 4x4 foot area is required, and you tend it without going outside.
It doesn’t matter if you follow laws in place that actually DO pertain to you, the laws of physics will determine if it works. Safe clearances have been tested, and are given without the need for you to test them. They are given in the stove manual, and NFPA-211 we all strongly suggest you follow was started in 1896 for a reason. It is updated every 3 years, and older publications are available free on line. That will prevent you from burning your home down. Some of us here have been burning in our stoves before you were born, have tried many things, and are speaking from experience.
No matter what you do, the wood needs to be dried first. This takes time. Start with getting a moisture meter. Cut, split, stack and top cover for months to years before burning. No matter what you use, you need to dry the fuel before it will work.
