Oh fruhagen I feel for you.
I'm finding myself being the constant voice saying 'give up, let go' on these boards and I need to be careful about that. Please bear that in mind reading this.
People can always refuse medical treatment, but they can't demand to have it (well, they can, but doctors can't be forced to do any treatment they think is not appropriate). If the person has no mental capacity for a specific decision on medical treatment, their GP or consultant can decide for them. This decision should be in their best interests, in consultation with loved ones, and the least restrictive option.
A LPOA means that, if mental capacity for a decision has been lost, the attorney becomes the decisionmaker on refusing medical treatment. They should then make the same sort of best interests decision.
In my view, the problem arises if you don't want treatment- the opposite of the above! I believe elderly people are grotesquely overtreated medically, in hospital far too much, and 'under cared for' if that's a legitimate phrase. My mother's life was saved after a brain bleed almost 18 months ago, for absolutely no point whatsoever. Her life is completely meaningless now and should have ended then. She has also since then had multiple courses of antibiotics, which in my view were cruel and inappropriate. We finally, finally got antibiotics crossed off her drug chart after multiple fights with doctors and staff. My sister and I have become tough and stonyhearted (in their view) but we know our Mum's wishes. I am lucky that I know this was her wish. Unfortunately I was never able to persuade her to give us POA for health. She also never dated or got her Advanced Directive witnessed, which made it useless. Nonetheless I am certain of what she wanted. They don't know her.
Doctors are too likely after a stroke to just say 'we put a PEG in after a stroke' (that's a quote from a consultant about a patient I was involved with). Ludicrous. The family had already stated as clearly as they could that they did not think their beloved relative, who lived with them all their life, should have a PEG. The consultant ignored this.
I think you were right about your DM. And I'd urge you to get your PoA in place and tell your attorneys what your wishes are, loud and clear. I'm afraid I think 'you can't do that to your kids' is simply ignorant. What i have suffered for myself and on my mother's behalf due to overtreatment and lack of a POA is close to unbearable. Far worse than grieving a short illness and a peaceful death - my Dad had that and thank goodness for it.