My first thought re using a dehumidifier was that they aren't really designed to put out cold air, just remove moisture from the air.
To cool the torroid, I need cool air and a lot of airflow (235 cfm). While an interesting idea, modifying a small dehumidifier to get me there seems like it would fall short. Maybe a 5000 BTU room AC appropriately modified to direct the air where needed could do it, but the penalty is probably 700-800 watts from the inverter output.
I'm thinking if I keep the relative humidity off an evaporative pad under 60%, I'll be OK. I believe the PJ is good to at least 85% RH. Summer in the SoCal inland areas sees humidity in the 15-20% range. It's pretty easy to get a 15-20 degree F temp drop by misting a cooler pad.
When the outside air and garage gets to 105F, I'd be happy to put 90 degree F air into the inverter located therein for a few hours. Obviously, I don't want water droplets getting into the inverter. And I haven't run any numbers to see what temperature drop correlates with a 40% increase in humidity off the pad. My goal may not be achievable.
Regarding the torroid in distilled water, I hadn't considered that reacting with metal might change its non-conducting properties. If we adequately encapsulate the torroid and attached wires somehow, I guess it really doesn't matter. I drop a small submersible AC outlet plug-in pump into my pool spa when it needs to be emptied. Haven't blown any breakers or tripped a GFI yet. Given the moving parts, that would seem an even greater isolation challenge. Yet they manage to get UL certification.