Sorry to hear of your poor pups dice with parvo, glad that he is recovered and on his way to full health again. Just to echo don't worry, these things happen, illness and quaranteen can interfere with socialising, but he isn't acting like a normal pup of his age right now anyway, he is still sleeping a lot, still weak and so really not mentally progressing for a pup of his age, which actually is a plus in another week or two he will no doubt have perked up and be acting as a younger pup getting used to exploring and finding an interest in the world, so up until the next couple of weeks he really is not missing out on his socialising, in a couple of weeks he will be ready for catch up and to be honest you can treat him then as you would an 8 week old pup.
Giving him confidence as already said is the key, others may not agree but I would not even carry him around for outdoor socilaisation until at least another 4 weeks, his immune system is not good, (not sure on his shedding of the virus and affects on meeting people with dogs so can't comment on that part but nethertheless I would keep him away from people who own dogs) if your able to use your garden I would use that time to get him ahead in little training and play sessions, make the house and garden fun for him, get him healthy and used to visitors and family members and after his first shot then begin to do outdoor socialisation. Get one of those baby carriers for dogs

you can pop him in and take him basically anywhere with you then.
Get him used to bangs and clatters, show no reaction and keep very upbeat around him so that the world holds no fear also when you first begin to socialise him outside he will look to you for guidance if your happy, he will be happy.
But, I really wouldn't worry, he is in a home with plenty of love it will take him a long way and he will catch up with everything.