If slice had a close friend who had his parents on DNP for years and they lost a shit ton of weight I feel like he would have mentioned that....
I think slice put his own mother on it bc he complained at one point that she out ate the dnp.
OP I'm nobody so take this for what you will - Dnp does have known health risks surrounding electrolytes, chronic dehydration, neuropathy, etc., but if your parents know about these and are willing to get blood work more often then, based on the info available, I don't see why they couldn't take it.
The question isn't, to me, whether they could or couldn't, but whether they should or shouldn't. It sounds like your parents aren't willing to do the necessary things to live a healthier life.
Dnp isn't magic, but it MIGHT help cholesterol, fat mass, obesity, and, theoretically, some forms of cancer that are partially fed by glucose. It has neuroprotective benefits that MIGHT help aid in the fight against dementia / Alzheimer's. It can help fight diabetes and prediabetes.
But what about general inflammation? What are they doing about that? I doubt your mother's carb dishes are helping. What about the forms of cancer that aren't assisted by glucose. Neuropathy? Altered vision? Dehydration? Osteoporosis? You asked about what else you could give them. I could say anavar or primo or tbol for either of them.. maybe cyp for dad, but what good will those do if they're unwilling to resistance train? Yes, they may reap benefits from these hormones but will it outweigh the negatives?
Have you thought about taking them to one of the hrt clinics so at least someone is consistently monitoring them? They may suggest for IV vitamin bags and inj curcumin with b vitamins.
You could give them antioxidants, help them learn to replace inflammation causing carbs with anti-inflammatory carbs. Switch to healthier fats. Find healthier alternative recipes to their favorite dishes.