Searching for advice or potential problems in future with design

[darkvalley]

Fortunately this has nothing to do with distilling, but with energy / heat storage, heat extraction and wood fire. Something I have a bit of experience in.

I fully agree with shady. Simple is better and if you go with a heat transfer system, that can go boom due to pressure, design a pressure less system. If the mechanics fail, all the water in the system boils off in stead of explodes. Refilling the system is much easier than collecting shrapnel due to a check valve failure.

Examples can be found online but commonly you make a t-section with a long standing pipe (directed to somewhere hot steaming spurting water doesn't cause injuries) Just ensure the length of standing pipe is quite a bit higher than the highest part of heat transfer loop to create sufficient pressure in the system itself / e.g. the pump will circulate the water but choses the path of least resistance. You will get corrosion in the system as it is open to the atmosphere but there are ways to account for that with annodes.

As for energy storage medium / transfer from the wood fire to the system, you could consider a sand battery setup. E.g. you heat up a large container filled with sand (setup around the chimney) and run through the sand a heat exchanger to the system itself. You can burn the fire as hot as you like = lower emissions, smoke, the sand can go up to 400 degrees Celsius and yields an overall higher efficiency. This is less stressful for the heat exchange (slower heat up and cool down)

Depending on the mass / amount of sand you heat up, the battery will have a constant temp rise (and drop) and will keep warm long after the fire has burnt down. More sand = lower peak temp means so you can actually play around to hit a sweet spot of mass heat storage e.g. 100 degrees Celsius.

I applied this theory in my own house building a rocket stove mass heater using fire bricks and a "bench" that sucks out all the heat from the gasses before they vent out. My exit gas temp is around 100 degrees Celsius. The thing has enough mass that it stays a comfy 40 degrees for nearly 48 hours with one burn. Naturally there is less heat loss that with an active heat exchange to a mash.

Robert Murray explains the theory of a sand battery using an ordinary electric heating element (for solar heat storage applications)
And also how to built a rocket stove:
And how to combine the two theories:

Hope I could contribute a bit to your project.