Take him to a junior puppy pre school. Find a delta society trainer who will get you through the puppy phase as well as the post abuse phase.

I've done quite a bit of study in dog behaviour and ran puppy pre schools for 10 years. We got a dog who was 6 months old who was covered in ciggarette burns.
I also have a labrador who used to be excited when people arrived and bites hands.

A few quick tips are to put something else in your pups mouth when people arrive, so we had a little box with old stuffed toys from op shops and we would put it in the pups mouth when someone knocked on the door, now she is 7 and rushes to get a stuffed toy when someone arrives. Give him a little sandbox where he can dig, and bury some toys half way and some treats. Instead of feeding him breakfast, throw dog biscuits out onto the yard randomly. Make him find his food... It will stimulate him and make him excited when you go.

He sounds like a good smart dog, and one that will be awesome once he has a bit more training.