I will have to ignore the image, as it could be construed as a copyright map.
I thought the official language in Dubai was Arabic, not English. Is the station really only signed in English. I would have expected:
name=الجداف
name:en=Al Jadaf
However the way it is actually signed should determine the correct usage.
Strictly speaking, you are probably right that the station should not be on the track, although I think it would be OK to do that an early stage of mapping, before all the correct relations are added. Mapping of a railway can start with just a single line, representing all the tracks, in which case mapping the station on the line is reasonable, but, as you add more detail, e.g. tracks in both directions, it can cease to be a good idea.
I would treat articles on underground railways as overriding any on ordinary railways; don’t expect the wiki to cover every case.
For the building, firstly is there really a sign on the building, with its main language being English saying Al Jadaf Metro Station? In particular, does it actually say “Metro Station”.
If you are going to do area mapping, you should map the the whole railway station as an area, including platforms and buildings. If there is a building within that area, building=yes is probably OK, although, if it is exclusively used as a railway station, you could be more specific. If it covers the whole of the station, it is probably the correct place to put the tags for the station. Unless the name of the railway station is also used for building when it is not used for a railway station, I would tend to leave it un-named. As always, you need to look at what is actually done on the ground.
My real problem with the building is that the railway line is mapped as going over the top of the building (building layer=0; line layer=1). Mapping that correctly will be fiddly.
I’m not going to look at the walkway in the image, but on OSM, the only obvious problem is that it does not connect to anything.
For the other details, it is really a question of how much time you want to spend. In the UK there are a lot of railways enthusiasts, who would want to map in a lot more detail than is useful for the general public.
Also, looking at this area more generally, there seems to be an extreme over-use of English, and a failure in many cases to have the Arabic at all. For example, I can’t imagine something described as an Islamic Hospital doesn’t have Arabic prominent in its signage. OSM is a map for local people not for English speakers, although it can include English alternatives.
In addition, I get a feeling that there is a tendency to want to name everything, which results in the name being constructed from meta-data.