Do not worry too much about atmospheric humidity that our analog/digital gauges tells us.
Forest scorpions such as Pandinus imperators usually spend most of their time hiding under a slate/log or burrowed deep within the substrate. What affects them is the moisture content of the substrate.
For forest scorpions, as long as your substrate is damp and not to the point of soaking wet, it is good.
Regular misting is only good if you wish to gain some muscles in your arms
To maintain moisture of the substrate, there's false-bottom setups or simply pour water directly unto the substrate (which only needs replenishing every 1-2 weeks)
For your 2nd question, search on Isopods (Tank cleaners for forest substrate)
Do a self-intro if possible, it'll bring better response to your threads.
Cheers