True, However, It does NOT run unattended, and is NOT a garage, its a metal outbuilding, not attached. It is not an issue for my insurance agent at all. Not sure why anyone would leave any type of solid fuel heater running unattended.
UP? The nearest futures price is $3.38. Guessing you don't farm. My Brother in law said at that price, it sits. around here, lots of folks heat with corn, corn boilers are replacing the outdoor wood boilers. I have not had an issue with clinkers, not saying I won't. Stove does not have to be shut down to remove, but if they become a problem, mixing a bit of oyster shell should eliminate the issue. Stove is rated for up to 20%, but I don't know of any elevator that will take it above 18% around here without a surcharge. Plus it doesn't store well above those levels, so I do not see it being an issue.
All corn stoves generate a nasty starchy clinker. Most stoves have to be turned off and let cool before you can pry them out of the bottom of the pot.

All of your fuel choice need to be kept DRY !
Wood pellet can be made from hardwood or softwood. You want hardwood.
If you are interested in trying to build something, look up rocket heater (a variation on a rocket stove) on the web. Lots of variation, but they all are pretty efficient based on the flue temp.