Hi Jon, I work a lot with the Ziatype and traditional Pt/Pd printing. As Barry S says above the traditional method is extremely simple and I would start with that. You'll find it much more predictable than VDB prints. But Ziatypes can be beautiful. After you get a handle on the develop out process, then you should give the Zia a try. The ammonium ferric oxalate would be the only chemical "wasted" if it didn't work for you. Lithium palladium can be used in the develop out process just the same way as the regular palladium, so it wouldn't go to waste.
I get a lot of humidity here in NY, but in the winter when the central heating is in full swing, it goes down to about 30%. Everything works fine at that humidity. I've come to the conclusion that too much humidity is a bigger problem with image quality. When it goes to 60% in the summer here I dry my paper a bit after coating with low heat. I get smoother prints that way. I think if you closed the door and ran the shower, for a bit, and had a cheap humidifier going you'd be fine. I have what is really just a cold water vaporizer, not an ultrasonic humidifier. It brings the humidity up very quickly, like in ten minutes. But I seldom use it anymore.
Here's how I would start, which is what I did when I first tried the ziatype. I coated a piece of paper and after a 2 minute rest I exposed it right away, with mylar protecting the negative. (If you use the same piece of mylar again, make sure it's clean and dry, so you don't ruin a negative, like I did,) Then I coated another piece and waited 5 minutes and then another, and waited 10 minutes and a fourth for 15 minutes. I found all the tests gave a good image. The one that I let dry for 15 minutes took a bit longer to expose, but it looked good. The one I exposed after 2 minutes was grainy looking. You of course will get different results, but I bet you get a good print. There are lots of Ziatypes in my gallery here, check them out. Best of luck and I'd love to hear how it goes for you.
Doug Schwab
Brooklyn, NY