I think the 'moisture control' is causing most of your issues.
In your situation, I'd probably just get more soil as needed, hopefully nothing extra to worry about. There's no great way to store it. If you get stuff called cactus soil, things will probably go a lot easier. Potting soil is predominantly tiny particles of peat, which lodge so tightly together that pots have no air in them. Add silicone crystals (the moisture control) and you can get root rot in record time. Roots need oxygen and moisture at the same time to function. That's not possible if whatever the mix is has too many tiny particles, the soil at the bottom of the pot will always be airless.
Whatever you decide to put in pots, don't pack it tightly around roots. Give 'em a chance to breathe (and yourself a break from such high risk of causing the roots to rot, 'overwatering.') The one thing potted plants need for people to do for them shouldn't/needn't be what kills them.
