Hi Jen
Hope you are still reading the posts.
Rocket stoves by there design influence the exhaust gases that allows the heat to be radiated into the room quickly before exiting the flue. This cools the exhaust gasses and thus the draw effect. It is one of the reasons rocket stoves fail. The length of the vertical stove stovepipe may be too short, and I my opinion should if it exited out of the building closer to the ceiling. This would help with the draw, when the mass is installed that also will help with the draw. There will code requirements in your area for how close you can go but there would be other options as well to meet the code. i.e. a vented fire separation space. The damper can also be used to control the draft if it is closed a little that will increase the flow pressure. Play with that a little as well.
The smoke detector most likely is an ionized smoke detector these measure small particles and thus the alarms. A photoelectric smoke detector would be better for this area as they detect smoke particles. There are one that are battery operated and/or power by the electrical system. The burning off of the metals will pass if not already.
Cheers
