Nuke them first. But corn cobs I would say are pretty pest free especially if you are collecting them from corn you eat off the cob.Yeah chopped up corn stalks are used succesfully as bulking agents in composting manure and even biosolids. I guess those would work too, but I have no ideea if those invite pests when used indoors..
Depends what type of a soil you have there.How much biochar would be good for a garden bed that never got any? And do I stop using perlite or I add both?
Mulch works good indoors too, i topdress every pot with an inch or two of pure sand, it really aids with distibuting water, blocking pests, and creates a water retentive structure over time and wateringsPerlite doesn’t hurt and if you still have that just mix it in. If you can you should mix everything together throughout, but if you don’t get all the way to the bottom it’s fine. The first 30-40cm is the most important and outdoors you benefit from mulch because it helps preventing evaporation of the water from the soil.