Jeff writes:

Also, I'm open to other thoughts/suggestions on mold/mildew remediation.

Most concerns about mold/mildew are neurotic fantasies.

Forget the humidistat. Relative humidity cannot be measured automatically,
accurately, quickly, *and* reliably enough by any reasonably priced device;
without all of these the control will be faulty and you will be worse off
than doing nothing.

Buy a programmable thermostat and program it to run at least an hour every
day. That should control humidity in any modern construction.