Steps to reproduce:
Load the save.
Take the blueprint from quickbar
Place the blueprint over the huge rock or spilled iron ore using SHIFT + Click

Expected:
Items from the ground (coal / iron ore) get placed into the unfiltered storage chest.

What happens:
Items from the ground get ...

Rules: To set the "leave Station when empty/full" rule, click on "Rules" in the trainlines window, set it for the stations, click save. Done. The first check for the rule will happen 4 seconds after arriving at a station, the next ones every 2 seconds.
If the normal waiting time is passed the ...

Could you explain why (if at all?) is the loop at the bottom necessary?

First of all, if you are ok with small (~0.2%) leakage of liquid into low priority output, you can use basic design:
http://i.imgur.com/nZA4ZBX.png

If you wand "perfect" 100% solution, then loop at the bottom is necessary ...

Let's say you are building an Advanced Oil Cracking facility to produce Petroleum Gas, but you also need Lubricant for some intermediate products.
If you don't have a lot of Crude Oil, you may face a problem when all your Heavy Oil is used by Heavy-to-Light cracking, and you get no Lubricant.

Here ...

It's usually called "speedrun":
https://forums.factorio.com/forum/viewtopic.php?p=34900#p34900
https://forums.factorio.com/forum/viewtopic.php?p=47288#p47288

Tips:
- steam engines instead of solar panels
- steel furnaces instead of electric ones
- no logistic robots
... and a lot of planning ...

What kind of openers are you guys using? How many burner miners do you tend to get before moving up to electricity? Do you use wood or coal for early fuel?

3x iron, 1x stone, 1x coal and 1x copper is enough to establish electricity.

http://imgur.com/akrJYZF.png
http://imgur.com/ffbb8Yt.png ...

Pretty fun challenge, indeed.

Yeah, you should definitely fire your train engineer )

Can be simplified to fit into 10x11 tiles:

How can I split "liquid" evenly into two pipes?

All smart inserters have the same wire conditions.
Important : do not connect existing power network to you main base. This build is self sufficient.
To set entire build on, put coal (or any other fuel) into two bottom steel chests, put ~10 stone ...

Hm. Do I understand it right: you put every bot into the roboport, until the port is full. Then there will be a bot in the smart chest and triggers an iron/copper inserted into the smart chest, too. Once the port requests again bots, the iron/copper is taken out of the smart chest and blocks then ...

With a setup like this, do you build in any kind of rate limiting? Or will you just let it go, until you have 1000s of robots flying around? :)
Limits on logistic and construction robots added to roboport:

http://i.imgur.com/xd3jaew.png

Let's say we want 18 logistic robots and 6 construction ...