Perhaps for the untrusted satellites? Did you remove them? How To Forget Untrusted Satellites
I think that just this exemplar is too slow, maybe it is a SMR.
Only for untrusted satellites, see the article above. The folders names you can see there: Satellite info (Address, ID, Blobs folder, Hex).
yes, it will reduce the load and maybe the node can finish the housekeeping faster.
Usually yes, because they would not compete for the same resource - the same pool, if you ran them on the one pool. And also any RAID with redundancy is usually working with the speed of the slowest drive in the pool.
Likely yes, you may also use rclone sync instead of rsync in the guide linked above, it could work faster.