Scared POM

Hi there,
I recently purchased a 6 month old pom and he is scared/untrusting of everything. I have received recent news that the dog was picked on by the other puppies in the litter.
some symptoms:
- dog will approach, but when you go to pet him backs up
- when you pet him, he lowers head cowers backwards
- if he believes you have left, he cries, a lot
- when you go to pick him up, he lies on the ground and
tail in between legs.

now that there is some background info.
my questions:

- how am I able to build up his confidence? activities? love?
- are there methods to help with separation anxiety based on his personality?
- any other suggestions at all ? or stuff that has worked in the past.

this is my first dog and I hope everything works out.

Thanks

Poms look like lions