Bay 12 Games Forum

traders care about relative profit not absolute profit in each deal, as said before, if you give them around 50% profit they tend to be very happy. I usually churn out tons of rock craft which gives me enough currency to buy whatever I want. If you decorate them with cut gems they become even more valuable. If you happen to have gold or platinum in large quantities, a handful of gold crafts will buy out any trader.

you first need to make the coffins, then build them, and then mark them as use for burial. Then a burial job should be generated for each dead dwarf as long as there are enough coffins. Eventually an idle dwarf will get around to do the burials.

I use 3x3 bedrooms for everyone, with smoothed walls and floor and rock furniture. Putting them in 3 by 3 blocks (with lots of doors) gives the same size as 4 5x5 rooms which I use for all my workshops.

Note that these are not really requests, it simply means they will pay higher than normal prices for these goods. Nobody gets sad if you don't sell them these items, just extra profit for you.

You experienced what is called a tantrum spiral. It is working mostly as intended and is one of the most common ways for fortresses to die. Essentially it starts out with some dwarf getting really unhappy (whether for a legitimate reason or not) and then doing something that makes another dwarf very unhappy. From there it cascades with exponential growth of unhappiness.

Not sure about the dirt roads. I think dirt roads will over time degenerate to regular tiles again and then stuff can start growing on the tiles. I've seen the first few tiles of dirt road disappear within less than a season.

As far as I know the skill a dwarf has in any of the health skills has little or no effect on the chance of the ill/sick dwarf recovering (insert joke comparing to real life here). I usually enable all health labors for a handful of dwarfs and provide a well equipped hospital close to a well. It seems to work quite well.

To get a basic hospital running just set up a hospital zone and put some beds and some containers (easiest are rock coffers) into it. Enable the various health labor for some doctor dwarfs, diagnosis is the most important, as every illness is diagnosed at the beginning and after every other step that needs to be done. Put some tables or traction benches right next to beds for operations. If you look at the hospital information it will tell you what materials are needed, if you have them available in your fortress, dwarfs will automatically bring them to the hospital.
After you breach the caverns all sand/mud tiles can grow underground fauna, normal stone tiles cannot. So you don't need to fear that trees will grow in your living quarters but this is useful for underground tree farms and underground grazing areas for animals.
Invasions are somewhat broken in 0.40 versions, you might get a goblin invasion of 5-10 goblins very early but once you made it through the first 2 or 3 years there seem to be rarely any invasions at all. I don't think anyone observed the typical 50-100 goblin invasions large fortresses suffered in yearly in 0.34 versions. Also invaders often seem to just leave after successful killing a few grazing animals without ever trying to enter your fortress.
If you don't have iron, then copper is almost always available, bronze is better than copper but it is much more likely to have some iron ore (there are multiple different iron ores) than the ingredients for bronze.