I’ve always been in a coastal marine environment that gets alot off humidity (+/_80% all the time) and condensation, even imho indoors. And you might not even see it.
What I’ve taken to doing is keeping clear plastic bags bags (-that nice sheet sets come in) & cigar boxes closed with paper towel covers on top of my more valuable steel hand tools inside (files, nips, clippers, pliers etc). I also have plastic trays with terry cloth towels laid over them. All of these go into a shallow drawer metal cabinet like an architectural flat file. I keep it closed at the end of the day, everything tucked away. I pull out what I need to work on for the day or task and then put everything back. Project tools might go in a clear plastic zipper bag with a towel wrap and remain on my bench overnight.
For myself, leaving tools on a convenient rack is destructive. Just putting tools inside a closed cabinet doors not work. An additional soft thick fabric cover inside did. It’s like tucking babies securely into bed in a cold’s damp night. I learned. However, because I was also teaching privately, it was really impossible to get students to do the same consistently.
The dry towels over all metal tools inside plastic containers has nipped the rust problem in the bud. I also keep a soft set of wire brushes (steel and brass) to occasionally detail my larger 100+ yo files.
I cover and protect my vacuum/ investment table, vulcanizer, polishing station, welder and rolling mills. My kilns, the same when not in use. The heating elements can slowly rust inside a kiln.
The saying that rust never sleeps is so true. It’s kind of a pain, but I have that giant cabinet right next to my bench for hand tools so it’s not so inconvenient. It’s alot better than discovering creeping rust. When I had to refurbish and then re- polish a year old planishing hammer, that’s when I started getting really diligent. I developed good habits with my tools.
The dehumidifier would be a losing war because the studio was almost 900sf and a half subterranean basement with ground level windows on two sides. Ocean on the sides within 2 blocks and a perpetual brisk wind that peels paint in the afternoon. You live in the land of inland oceans.
My new studio is in alot cooler and similar damp environment in western washington and not currently set up, but I have lots of small exam rooms (it was built as veterinary clinic in 1933). The daytime temperature sits at 38F for 5 months and the dewpoint at 43F. Everything is damp. The first thing after the new roof was getting the older propane furnace in perfect working order, which helps immensely. I can’t wait to finish the glamping phase of our life in (architectural) rehab… LOL
A good small quartz heater or electric oil radiator, those are both good space heaters. I would suggest those over any baseboard heater set up.
Rigid 3+inch roofing foam or R19 + insulation firred in is nice for a more constant temperature. You might get good rubber insulation mats for your floors as well.
And you might want to come up with a service sink set up some sort. When you’re not running water thru it into a bucket… you can make a cover for it and it’s an extra counter/ work space.
Warm, comfortable and dry… you and your tools in winter… nice fans in a reostat for ventilation in summer when humid air is so thick you can cut it with a butter knife and frost a cake. I spent about of time visiting family in MI “thumb” when I was a kid. The humidity is comparable but alot more uncomfortable.
You’re going to have alot of fun! Best of luck.