Brilliant musings. I'm one who has said 'Dumbledore was going to die, anyway', but what you are saying is definitely significant.

I must admit, I've thought the poison to be one of the mind; clearly Dumbledore was affected on another layer than simply physical death - he did recover somewhat after finishing the potion and held his own against Draco before Snape came weilding his wand.

He was definitely 'dying' in the magical sense, too, hardly able to hold the ring of fire around the boat, Harry having to Apparate them back to Hogsmeade. That all twists in, of course, with your ideas on the psychological weakening...

And Im rambling so I'll finish with, great ideas here well done. Hee :)