
So sorry you are having this trouble. And I agree, much as you should be able to keep a puppy going with glucose and warm water (no point really if mum has milk), something isn't right with this puppy. Is he warm - I'm sure you know once morbidly chilled, they won't nurse. I never got to grips with tube feeding so I sympathise. If a puppy is strong enough he should nurse.
We had one disasterous litter (veterinary incompetence) where one of the 5 survivors had milk coming through his nose to the point despite our best efforts once we got them all home, he didn't survive. The wretched people had tried bottling the litter once they were able to be born via C.Section - all they needed immediately was to be in warmth to recover their ordeal and 'ordeal' it was because the C.Section was delayed to the point that 4 of the 9 puppies were doa, to be joined by this 5th one. I wept because he was stunning - almost all white with a black head and small black patch at the tail set on. He'd have had black ticking on the white eventually too.
Me thinks the vet should take a look at him. And the other puppy + mum too of course.
When breeding goes right, it's such fun. When it doesn't it's heartbreaking. We had a wonderful time with a Christmas Eve (Sectioned!!) litter one year. After the trauma of her needing the Section, thank heavens it all went well 9 puppies and us shut in the warm with it snowing like crazy outside (Canada.)