I'm no expert on
RMH but at the basic level it looks to me like your really trying to push and pull the design I some ways it wasn't meant to be.
The bed has a ton of surface area and the flex tube creates a massive anoint of resistance to flow at that length probably we'll over double that of standard round pipe. This to me is an area of major inefficiency. I doubt it will ever function safely without the fan.
The extended heat riser and barrel might make it initially draw better but is probably also consuming more
energy that you want to transfer into heat in the process. So I'm wondering if this is a net loss of usable BTUs rather then a net gain? The thing is a
RMH is designed to be about as close to maximum efficiency of a
wood stove in its basic design. I'm doubtful there is room to make it any better and still have net gain?
The forced air aspect to me looks is like adding a turbo to an engine and considering a RMH is already close to max efficiency all the turbo is gonna do is suck up more fuel meaning you'll be feeding this beast like crazy. This may mean more heat as we'll but RMHs at their basic level already operate at close to the maximum limits of the materials so this could be why it's eating itself up on you. So what happens when it's the middle of winter and your peer system fails for 3 days? You have a RMH that doesn't work and a cold house.
Finally the cheapest energy is the energy you don't use. I'm assuming you've already upgraded the building envelope to be more efficient? Typically churches are not efficient structures and need a lot if insulation and air movement to be comfortable and healthy places to live.
I know it all sounds negative but maybe issues your going to have to deal with to be successful. Good luck and enjoy the journey.