Danger, Will Robinson, Danger!!
I think you're confusing two processes and might want to consider tossing the spalla. There is no fermentation for whole muscles, after curing you just place the meat in the drying chamber and away you go. You're temperature is way too high and are risking case/exterior hardening. The fermentation is for salamis - ground meat in a casing.
According to pg. 78 of
Salumi you want your fridge at 55-65ºF (12-18ºC), 70% RH and some air circulation. Then all you do is wait for 30% weight loss.
If you're using the recipe on page 93 of
Salumi there's no mention of fermentation, just curing and drying (i.e. controlled dehydration). Botulism could be a concern if you deboned and rolled the spalla but is unlikely if you left it bone in and left it in its natural state. But with those high temperatures, who knows what's growing on there.