I think we can ease up on Ophelia a little. It sounds like a pretty complicated situation and that Ophelia's trying to work through a lot of stuff.
From what you've posted, it sounds like you're in that rough patch of life known as parenting a two year old (
), and the whole food sensitivity/allergy thing is a total pita that requires a level of vigilance that's very tiring.
Ophelia, when do you next go to counselling? Can you bring this up as an issue there? Maybe a third party can have some influence. What about DH talking to his pharmacist?
I don't think the meds being left out is in any way negotiable. Can you try this with your DH without setting him off:
"DH, I'm really trying to see your point of view on a whole lot of things. The fact is that two year olds get into things, and that medications can kill a child. If something happened to DS because he got into your medications, it would do irreparable harm to our relationship, to your sense of well being, and would likely lead to charges of child endangerment and involve both the police and CPS. This is not a hard situation to resolve - your medications simply need to be kept in <insert location> all of the time."
The other thing to consider, Ophelia, is that if something were to happen to your child due to his getting into your DH's meds, you could be charged as well for child endangerment/reckless disregard. This is just a bad situation all round.
I hope you're safe with this man, and I hope you find a way to a better place. Take care of yourself.