Most of the things you say are fairly correct, but those things absolutely undetectable with current technology. There are projects looking for all the things you say. There's not much to report yet, and no real timeline to find anything.

There's no way to detect the magnetosphere of small planets. Only a few hints in giant planets close to their stars. There's no idea on the table to fix this.

Iron content is probably fine. That's not an issue. Most stars that we can study are nearby and have similar compositions. So far, all transiting planets with RVs (so with radius and mass) have densities consistent with iron cores. The problem is most planets in habitable zones don't transit so we can't really be sure.

The existence of the planet and position within the system is one of the few things we can detect. And only within certain constraints.

Just to make an example. If we had observe the solar system since ~2000 with RVs, we would probably think it is a 1 planet system (Jupiter), or maybe not even that because its possible to mistake Jupiter's signal for the signal of the stellar cycle. It would be difficult to convince the community that it is not a false positive caused by stellar activity.