1. Fishing is planned and not too far down the roadmap :)
2. There could well be a tree planter at some point. There's going to be giant mushrooms that can be used in place of trees, so maybe they can be cultivated.
3. It is a long time on purpose for the mushroom farms, but then they produce several crops of mushrooms so they're a pretty good investment.
4. Yep the door placement definitely needs this improvement.
5. This one's weird, maybe a bug. If you get into the same state again, would you mind emailing the save game to firstname.lastname@example.org and I'll look into it
6. Stockpiles are a bit under-developed right now too, there'll be more controls over what can go in each one rather than the arbitrary 4 there is now.
8. Also on the roadmap but not in yet is a "ceiling view" to show what has a roof and what is supported or not. The rules are a 7x7 area mined out by the player will collapse if there's no walls or supports. Doesn't apply to natural caves. Agreed it's a bit of a secret mechanic right now!
Thanks for the feedback!