1) all things being equal, what RH% would you run your chamber if you're curing a Capicola and salami at the same time? I see several recommendations for 55 degrees and 75% humidity for the coppa, which might be a tad lower than salami though I've seen those numbers for salami too.
True answer....it depends....
Meaning, it depends on where you are checking the RH%. 75% at the top of the chamber on top of the top shelf? No problem...that will put the RH% 80-83%RH near your Salami and Salumi.
Evan Gramm is an old member here...he posted some absolutely beautiful salumi with no case hardening. When asked, he said he runs his chamber 80-85%RH. If you drop it to 75%RH you will get case hardening.
Home chambers are imperfect. Generally the air flow in most refrigerators is too fast. This is compensated by the long rest period between cooling cycles. I've toyed around with the use of a fan on the top shelf blowing directly on the ceiling at very low CFM in order to simulate a commercial drying chamber...the blades were barely turning...still too much air flow.
Every chamber is different, so you will have to troubleshoot it...which is difficult having never done this before.
There are trade offs... if you target too low an RH% too soon, the dehumidifier will run almost constantly trying to pull the moisture out of the unit. This will raise the temp. in the chamber faster, thus the unit will run cooling cycles faster...thus in an effort to target a lower RH%, you will dry the surface faster because of too much airflow from the unit cycling too much. It is all a balancing act.
Outside of a home drying chamber, I'm sure 75%RH will work just fine, but I find it impractical as mentioned above...