Think of cultures as a microbiological as a territory battle. If one thing is killed off, another can inhabit. When you cooked the already mesophilic-cultured cashew-peanut milk, that killed your culture. In other words you only see less than half the benefit of using it. I recommend not cooking it a second time. The mesophilic culture will continue to develop and age the cheese, and where the culture exists on the inside, mold cannot get a good foothold. I would set the culture in and make sure the pot is covered without any lifting of the lid until the end. Every lid lift can waft in bacteria and mold from the ordinary air.
So yes you're onto something with your concern about good technique. I make vegan cheese wheels, and have microbiological experience. I feel that by putting it into cheesecloth and hanging it up to dry, that in itself is giving your work huge exposure to the air. Those holes in the cheesecloth may seem small to us but to a mold or bacterium they are huge and easily populated. I favor using a more enclosed method like springform pan or maybe a simple cheese press.