Palytoxin: don't boil your rock, don't treat it with acid, if you absolutely must sterilize something, use bleach, which will denature the palytoxin. Or just...don't have zoanthids. Non-palytoxin coral allelopathic chemicals can be removed by running the water through carbon and using a skimmer.
Mycobacterium marinum: wear gloves. Just wear gloves. And Wear Your Gloves. You most likely won't be able to prevent it from entering the tank, but wearing gloves (the thick kind, not the surgery kind) will prevent you from getting cuts. And if you have an open wound on your hand/fingers/arm, don't work in the aquarium. And please don't suck on the hose to start a siphon.
I feel you on the OCD/anxiety. I've heard good things about cbd, other anti-anxiety meds, and cognitive behavioral therapy (what I do right now) as well!