Micropore is too much for a fruiting tray, you will get some gas exchange but no fresh air.
Buy some white filter floss for aquarium filters, squeeze it into a plug shape and pull it into the hole.
Agree, another cheap option is buy some synthetic pillow meterial from Walmart. Or buy acheap pillow. And take roughly a handful and lightly Jam it into a 1.5 inch drilled hole right at Spawn level because co2 is heavy. And put a small 6 or 12 inch fan just in the room pointing far away from your mushies to get the rooms air moving
If you have too much air flow you'll see your medium dry up near the holes. Put more pillow material or less air flow in the room
And I'm confused about you saying this part
So I had a humidifier in the still air box which had the mini monotub. Humidity was at 99%. So I took off the humidifier but the hygrometer is reading 67%
The part you need to worry about is successfully making strong fast colonizing rye Spawn... In you still air box. I would just spray h202 on the sides. Never mind putting a humidifier in your still air box blowing all sorts of shit around.
After you injected and colonized your jars. You can do this in open air really if you make injection lids with RTV silicone and tyvek air filter
After you have fully colonized jars... And given you use a high ratio spawn/ horse shit combo. as your not working in a healthy clean room environment... You should be using maybe 30 % Spawn /70% shit
The more Spawn you put the faster it will colonize and all your really trying to do here is get you mushrooms to out race the bad bacteria and once your medium is totally colonized your pretty safe.
If.... You don't break the medium in half ... It happens don't pick it up weird.
Or if there's sitting water
Or if you run it too long it eventually runs out of vigor and other shit lives off all of the acidic yellow by product and the spores and exposed food.