Good on ya jigsaw for taking him on. His feet will probably never come up 100% tight, but they should do for what he wants to use them for. I've taken in dogs that had never seen the outside of a kennel at 11 months old, (lurchers), and though their feet dont' come up quite right you should be able to see the difference in them after a couple of months: steady road work is the best., but watch the pads don't get sore. Dabbing surgical spirit on the pads once a day, not too much, will help harden them up.
Just sitting with the dog in its run will help too: just go in there and talk to the d