I'm trying not to overreact here since you've only asked for help on the medicine issue, but your post is raising some major red flags with me.
Playing 'games' about 'repercussions' isn't being stubborn, it's being abusive.
Doing things to spite you for-e-ver isn't a personality quirk, it's abuse.
Making you life in fear of his reactions is abuse.
Risking your child's life to be 'right' is not the action of a rational adult.
At the very least if I were in your place I'd have a secret separate bank account and would tuck as much money in there as possible.
(ETA: and yes, that is the not-overreacting version. the over-reacting version was to tell you to run, but I don't think you're in immediate danger from him)
I just can't wrap my head around your dh's reasoning. :
The fireproof safe thing sounds like it's at least a good temporary solution. I think that if I were in this situation I would have to give an ultimatum. I would either threaten to call CPS myself or leave, I guess. I don't really have any advice other than some kind of lock-box or a shelf that's up high.
I mean, you can't just leave without getting the authorities involved since he'd probably get visitation and you wouldn't be there to keep your child safe. IDK?? What would he do if you told him that the issue is serious enough that you'd consider calling CPS? Would he suddenly get how dangerous it is or would it just get worse?
This whole thing is truly unbelievable. I'm sorry you have to even consider this at all.
Oh, I just thought of something that could at least be a solution if he'd go along with it. I have an alarm clock that you set and it will stay set even after you hit the off button. So everyday at the same time it goes off unless you actually turn off a switch on the side of it. Pressing the button only turns it off for that day. It plays CD's so maybe you could get something like that that you could set for a specific time and then make your own CD that says something like "Take your meds" over and over again???