The broad at the store should have also sold you some worm castings; you need compost in your mix for it to work. You want at least 1/3 of your mix to be active compost. EWC is the best form of compost to use for cannabis and the fresher it is the better.
"Cooking" is just giving time for the ph to normalize after what you added in. Usually adding a bunch of organic matter will drop the ph a bit. You also would need a good quality soil probe to check it at the root zone with any kind of accuracy; runoff tells you nothing useful. I don't have one myself but if you just wait 30 days after amending the soil it should be ok to use.
Mold is not always a bad thing but depends upon what kind it is. If it is white mycelium breaking the surface that's good. If it's blue or green that could be bad especially if it's been kept very wet for a long time inside a sealed container. You might want to turn it and give it a whiff; if it smells bad like a stagnant pond it could have gone anaerobic. You want it to smell earthy like humus; turn it over every so often and let it get some air.
