About the 5.26 lbs propane tank for jewellry soldering?

Well the fire department said it was OK but how far away is the dept from your home? Added to the fact that you are not insured in case it blows would be another thing to consider. If it were me I would try to find someplace away from your home, perhaps build a small shed with windows to do your work. I feel sure you would be much safer in that condition or see if there is someone with a building outside their home they would let you use, but they would be skeptical about the tank.