I have been using an outdoor wood boiler since 2006 and I really like it. One big advantage of this is that all the mess from the wood and smoke stays out of your house. I have found that the type of wood really doesn't matter much. Anything will burn in it. I do realize that hardwoods yield more BTU's than pine, however, it is nice to be able to go through the woods and clean up any kind of dead or blow downs and make use of them. Another advantage is that I can heat multiple buildings with one unit. I currently heat a 1858 Brick house (3 stories) and a new garage (26 x 40 and 2 stories). I burn about 35 cords of wood per year. I will say that if you don't have a lot of time to cut, split and stack the wood, then a boiler is probably not your best option. Also, if you want to leave for a few days in the winter you need to have someone come and keep the fire going.
As to the rest of your post, I do not have any knowledge. Sounds like a fun and interesting endeavor though.
Good luck with it and let us know how it turns out.
Case 530 CK backhoe, JD 1010 crawler with 6 way blade and winch, 1946 JD model A, 1928 AA Ford Doodlebug(in progress) and MM skytrak