Welcome to the forum bro. I solved my heat problem with propane tanks, sort of. My current project, and has been for the past year, is to modify a 20# cylinder into some sort of useful stove or heat appliance. To that end, I need 20# cylinders, obviously.
Two local hardware stores (same owner) fill tanks and charge the customer $3 to take expired or rusty tanks off their hands.
Their supplier has since tripled the charge to take away said expired tanks, creating a challenge for the stores. I haul them off for free, then burn off any propane left inside to heat the shop with a small catalytic Mr Heater and a modified unit heater hanging from the ceiling. Once empty, I pull the valves and turn it upside down for a couple days before I slice it up with the plasma cutter. I end up with something along the lines of this https://www.youtube.com/watch?v=rmgM9Lzmzz8
albeit much more durable.
Probably violates some DOT or DOE rule, but since I'm saving the owner a big headache and big bucks, all is well. I have enough gas for the winter, but then my shop is 1/4 the size of yours.
To speak to your issue, I would suggest a wall-mounted Rocket Mass Heater. Most home applications sport a bench or bed for thermal mass, but the shop would benefit from the drum out front with the heat pipes and mass arranged vertically behind. Wood pellets or corn would be the simplest, but properly done it could be fired only twice during the day and make all the heat you need.
A free standing rocket stove like Z's would work well, but requires more attention. It's a trade-off; hands on for more minutes in the day, or invest the time and materials for the RMH and leave you to tend to business.
Turtle, gassing it