Do you think it is appropriate for a hospice nurse to hint around at how much of a patient’s medication it would take to kill them?

That topic should never come up unless the patient explicitly requested the information, and even then really only in regions where it would be explicitly legal (in any formalized euthanasia regulatory environment) to aid any patient of truly sound mind to pursue that path if there is really no bearable alternative.

Especially for healthcare professionals, they don't need to stray into the weeds with editorializing or whatnot, with any talk that is not directly helping the patient in that moment or a direct but limited response to any casual conversation the patient initiated. If the patient starts talking about the weather, instead of their illness, I would think the healthcare professional should respond in a well-mannered way but not then stray into darkness like "you know, when it's storming, if you stood next to a tree ..." ... as long as a patient is clear that they are still trying to remain in this world, the healthcare professionals should only be working to help achieve that and to comfort the patient, not distracting them with anything useless to those goals.

And hinting is always BS in any context, everyone should always come out say what they fully mean and want to express, directly and unambiguously.