Surely this whole debate is moot until we have the type the OP is asking about ( maybe his/her handle is a clue).
10,000', or less, for depressurization.
The 17,000', 25,000' etc restrictions are for terrain restricted areas.
That doesn't apply to all aircraft, some have an initial descent to FL150 (terrain allowing) and only a subsequent descent to FL100 when fuel vs. range to alternate allow (think overwater mid-ocean,ETOPS .... and yes it's in at least one aircraft's FCTM/FCOM).
While there is a possibility of decompression sickness for any altitude change, the possibilities of it occurring from an RD are extremely low
Maybe, but you can certainly start getting the intial symptons ( joint/ache tingles)... in any event I've never ever heard of perfroming a stepped descent simply to allow passengers to adjust...and you're going the wrong way, so to speak, to need for decompression/safety stops.....
As always I'm sure it's all in the relevant FCOM.......