Kaitlin, I'm sorry to hear about your infestations.

1) There are 2 camps here, 1st are the ones that use Imidacloprid insecticide, all you need to do is follow instructions and mix insecticide with water, water your plant once a year. When your plant has absorbed the insecticide, you will notice the infestation will stop. This is only a good preventative measure, if your plant is seriously infested, you might want to consider tossing the plant away and re-try.

Camp no 2 exist, because chemical insecticides will keep GOOD BUGS, ie bees, lady bugs, even through bloom. So there are natural ways to keep pests at bay, I've tried them, but there aren't 100% effective. Here's one -- dust Diatomaceous-Earth into your soil. It dehydrates the armor of mealy bugs and is completely natural and harmless to your plants.

2) I spray premethrin and manually remove them by sight when possible -- retreat in 2 weeks, because eggs are immune to treatments

3) Mildrew, fungus, rot are all conditions of poor soil drainage and high humidity. Succulents are desert plants that thrive in dry and arid environments. Read more about gritty mix and watering techniques to prevent this is critical for healthy succulents, and healthy plants generally recover better than weakened plants.

Best of luck, Bernard

More on Natural Insecticides here