I might be able to help with the pole question. I'm a mechanical engineer. Though structures are not what I work on, I know enough to be dangerous. I wrote up a little analysis helping another DIY person with poles once. Let me try to find it.

I wasn't able to see your pictures on instagram. Are they posted anywhere else?

poly fabric sounds like a good choice. You can get it in lots of different weights. Though for a large structure like this you probably don't want to go too light. Silnylon is popular in the backpacking community, though it is not fire resistent and it absorbs water so I don't think it would be a good choice for this application. Dyneema is another popular choice for people with deep pockets. It would be very light and wouldn't absorb water. I'm not sure how it would do with embers but probably not very well. The cost of the fabric would turn this into an ultra-luxury item. I think using the silcone mat for a chimney collar is a great idea.

In terms of taking it to market, many of the cottage tent manufactorers are now getting small runs produced in Asia, so I think their are opportunities there but I can't give you advice beyond that.