You can remove all of that to satisfy `vrms`, if that's all it complains about.  However, the real RMS would, I am certain, inform you that there is no way to make the pi truly free, since it requires some proprietary firmware in order to boot.  I mention this because it is always possible that in the future the virtual become more real, in which case you will encounter some insurmountable obstacles.  Right now `vrms` presumably does not check for such things, and they could be easily concealed anyway since they are not required after the kernel loads.

> 1. Regarding all these firmware-* packages

Those having nothing to do with the firmware mentioned in the last paragraph.  They're binary blobby things that can get included with the linux kernel due to the difference between Linux Torvald's and Richard Stallman's attitudes toward open source licencing.  At a glance, most of it probably involves wifi adapters, but in any case, they are not crucial to the operation of the Raspberry Pi. You would either know if you need them, or easily recognize that you did.

> 2. What would I lose exactly with removing pistore

I've never used pi store, but not because I have anything against it; I use google play on Android, etc.  There are [surprisingly few references][1] to it here.  Once again, certainly nothing crucial and you will know if you do.

> 3. Is there anything vital that ships on the standard Raspbian that depends on oracle-java8-jdk? Or on wolfram-engine?

Is Oracle java really in the current Raspbian image?  Anyway, nothing could possibly depend upon it since Debian includes a FOSS java ("iced tea"), and the system doesn't use java for anything anyway.

Wolfram-engine was added by default to Raspbian (it's not in normal Debian) for the Pi Foundation's own mysterious reasons.  If you don't need it, you can remove it.


  [1]: http://raspberrypi.stackexchange.com/search?q=%22pi%20store%22