You do have a pretty unique situation as far as tire needs go and I agree at this time there is no incentive for fat bike tire manufacturers (which is already a niche of a niche of a niche industry) to create a really heavy duty flat resistant fat tire.

I'm riding the Surly Bud and Lou in the winter and the knobs are ginourmous. They keep the casing off the ground and just roll on the knobs even with my fat a$$ on the bike. You pay a price on blacktop and hard pack dirt as the rolling resistance is higher., but so what. The traction is amazing off road and in the snow. The Surly Nates are very similar to the Lou's and might give you that type of clearance and flat resistance with the big knobs. They have bigger blocks than the Husker du's or the Knards (which look pretty sweet though). The Surly Black Floyd's are really a street tire, and might be thicker than the Larry's but may not give you the traction off road you also need. There are also 26' x 3+" cruiser tires with flame treads and stuff which might be pretty robust on the street, but again not give you too much help off road. Unfortunately as you know these tires are wicked expensive, even the 27tpi's which might be better for you are in the $90 range, AND if you are riding them on the road half the time the treads are going wear far more quickly than off road. I wish I had better suggestions for you but your specific needs really are a bit of an outlier. Don't give up yet!