Welcome! I'm fairly new myself, and have been going through some of the same questions for the past few months.
Eike has already covered most of your questions from a technical standpoint, but I can jump in with some related information from a regional standpoint that ties into some of that, since you appear to be a fellow North American.
Context to be aware of - OpenRailwayMap started as a German project and spread from there, and that's how the ORM tagging scheme started as well. From what I can tell, most of the English wiki translation was done by Brits. Overall it's very cleanly done and sensible, but there are some fundamental concepts that just don't translate right in North American railroading from either German or British practice, and some others that we've only recently (last few months) really started to hash our way through. Your #1 question has actually been a recent topic, and actually got covered in part by a pretty cool international web/audio meeting a dozen or so of us got to participate in back on 7/4, so a lot of this stuff is pretty fresh and not yet documented. That's also why we've got some really *big* holes in how the map still shows up in NA ... giant things like having no functional line labelling at all to speak of in NA, because the European tagging scheme as it relates to how they actually label their lines is completely different (and the team doing the rendering had no idea until June that what's done now doesn't work for us). That was probably the biggest topic of that 7/4 meeting.
Wiki progress comes in fits and starts, since we're all volunteers and it sometimes comes down to "I can map with my free hour today or I can *write* about maps."
A few of your more specific questions that I might be able to add on:
1. This is definitely one where the concept didn't translate well at all. Basically, yard is our catch-all in NA (everything that isn't schedule or train order controlled mainline according to the FRA in the US), and internationally they make a distinction between yards used for freight classification (railway=yard) and yards used exclusively for storage or maintenance (railway=service_station) that we really usually don't. I personally don't necessarily see an immediate value in the distinction, but since they render similarly and the international tagging is a little more granular, I can't see any drawback to tagging it the way it's currently written. That seemed to be the general consensus at the meeting, too.
2. This is intentional. There are a lot of railway yards that are long, skinny, and curved. If you placed the label by having the map software do something like calculate the geometric center of the area, on a long curved yard your label might not even fall anywhere within the yard. So, all location labels (stations, yards, junctions, and control points ... or "Operating Sites" on the wiki, which is another German term that really doesn't actually translate to English at all) are meant to have one node to serve as the operating site labelling point. Essentially, this makes for a better, more readable rendered map. (I started a draft for a new NA wiki page last month to start trying to clarify and illustrate issues like that, but got busy at work and had only finished about the first quarter - the draft is on my user page at
https://wiki.openstreetmap.org/wiki/User:Nathhad/Operating_Sites_and_Interlockings and the third illustration shows what I was describing with the curved yard.)
3. I haven't seen this one discussed yet, and it's a really good question. These really *aren't* considered yards in North America that I've ever seen, even though they are operated under yard rules. In the real world, we tend to give them a more specific designation here than just yard, similar to "service_station" being more of a German-specific designation. The Wiki currently calls for tagging as man_made=container_terminal (
https://wiki.openstreetmap.org/wiki/OpenRailwayMap/Tagging#Container_Terminal), which I do agree with, but as far as I know the name for it wouldn't currently render anywhere in OpenRailwayMap. That's because in the international scheme of things these would be considered part of a yard (with a railway=yard operating site note to label it), not a freestanding thing. So ... to be determined?
In general on the rendering, that's very much a work in progress too, because the team that makes that happen just completely switched rendering engines a few months ago due to some software in the old stack being deprecated, and had to completely rewrite the rendering scheme as a result. There's a lot left to do on the new scheme write up, so it's hard to tell which things are intentionally not rendered, which just aren't implemented yet, and which ones are local issues that the rendering team didn't even *know* were an issue or question here (like track labelling in North America).