Hey Noisy, all the best with your grow project, this species is definitely worth the effort.
I'd recommend checking out the attached grow guide, this is what I used with success in the past. The author has a youtube walkthrough guide too.
Because it worked well for me I've stuck with the easy cook brown rice/manure combo.
What filter is in place in your jars? Humidity of incubator shouldn't really make an difference, although wet filters can fail and allow passage of microbes, which will be more prevalent in a humid atmosphere. So dry might be better, you can go up to 27 degrees C. but don't exceed that.
Yes you want to definitely inoculate your bulk substrate with your grain spawn in a sterile environment, and make sure you have optimal ratios of grain spawn to bulk substrate before attempting this. C. cyanescens grows and fruits quicker than P. cubensis but it tends to succumb to mould sooner than the latter. A thin casing layer of moss peat/lime is also a necessity to initiate fruiting (prep instructions are in the linked guide).
I've never used straw, but I too have heard contamination can be an issue with it. So maybe something to experiment with later down the line. I've not experimented with bulk substrates personally, I simply lay out and case the contents of my fully colonised grain jars.
Copelandia likes high humidity but also lots of fresh air exchange, high CO2 levels can have a detrimental effect on fruiting. One way of achieving both high humidity and good air exchange is to place your fruiting tubs in a large fruiting chamber (with rows of small holes in the side), the bottom of which contains water saturated vermiculite. In this place a large air stone or two, connected to an aquarium air pump. When running this will raise the relative humidity and also generate air flow.
I think you are fine to fan, I think directly misting the mushroom pins once they appear should be avoided though.
If you're unsure of anything, lots of good info on Shroomology forum, a good place to ask questions of experienced growers to, quite a few peeps on there have experience growing Copelandia/Panaeolus.
https://www.shroomology.org/
Anyway I wish you all the best with your grow!