The hoppers are unavailable new anymore, I think anyway. They were over $200 for each half when they were. They do alright without a hopper too on coal, just a little more work and shorter burn times. You should have anthracite coal available somewhere near you if you are in SE MI.
You need a special glass for coal. Dont reorder those strips. Expensive and dont last. I'll dig tomorrow for the info you need on the glass. The glass will soot up quick with wood, be warned.
If your going to burn wood you need a protector in front for the glass. I'll take a pic tomorrow of what I did there. You may be able to dream up something better than what I did.
unfortunetly my grate got cracked this year or late last year somehow so its on borrowed time. Its still functioning but when it breaks its done burning coal. I'll put in a shed and burn wood in it. With the design of the stove it is likely from ash buildup under the grate. You never want the ash to get up to the grate or even real close. That can be tough to do because its a shallow ash pan but you have to keep up with it. Thats probably the worst part of the stove, how shallow the pan is. But for what I paid for it the stove did alright and will last a long time in the shed so its all good.
I know hardly anything about your air intake question.
Heres a link with a little more info you may be able to use from a couple years ago. Nester Martin Coal stoves ?