This poor baby should still be with its mother that is why it is crying.
The pup also needs feeding regularly through the night as well.
Is the pup taking enough to eat and drink?
As regards its poor tail the pup should be checked by a vet.It should be checked by a vet anyway and be given worming tablets every 2 weeks.
By day carrying the poor pup in a sling so the pup has human contact will help.Sometimes the ticking of a clock in the bed can help.
Is the owner able for round the clock care because this is what such a young pup needs.

Hi..get mini puppy food and soak it before feeding for at least another week..leaving a light and radio on can also help

Would second everything said by Dianna and Kay. Its VITAL that this pup is brought to the vet for a full check up – this should also hopefully eliminate anything that may be underlying. Are you in a position to take the pup / its owner to the vet? If so, you should mention that owner is a pensioner as there are often special rates available to OAP’s – many via Dog’s Trust who work in partnership with local vets to ensure quite substantial discounts for many things including vaxing, chipping, spay / neuter etc……
Viz comforting the pup, you could also try a gently heated hot water bottle for warmth and comfort placed in his / her basket. Its important to ensure that the bed is not too large as it will not keep the heat for the puppy. With the hot water bottle, make sure not to fill with boiling water and follow any instructions on the label of the hot water bottle. We got one in Tesco (Clearwater but Im sure any of the branches have them) reduced down to approx 4E (less than half price as they’ve xmas designs on them) and we found it brilliant for the puppy we were fostering, a real comfort. You could also add to its basket some form of stuffed toy but remove the eyes or any other bits that could be obvious choking hazards – again, we found this worked a treat with Smudge. The radio and clock are really excellent for them as the tick tock of the clock is nice and rhythmic a bit like mum’s heart beat and the radio provides not only comfort and stimulation but exposes the pup to the regular sounds of the day’s activities without being threatening so it should desensitise puppy somewhat. May I also suggest monitoring of the situation just to make sure that the puppy’s owner knows what he / she is doing as he / she may need a lot of support with the puppy, especially in the early days…….. Best of luck and keep us all posted on how puppy is but dont delay in getting the pup to the vet please!!!!!!