Sounds like you're doing great with the syringing. I know it's hard but it's so important.
Does he live outdoors? If so, I'd be inclined to keep him indoors; firstly to be able to monitor/care for him more easily and secondly to ensure that he's kept nice and warm. I'm sure someone more knowledgeable will correct me if I'm wrong (I'm no expert!) but I think it's generally recommended that a post-op piggy is kept in a smaller than usual cage, to limit his movement, especially with a wound that large.
With regard to pain-free cuddles, do you have a cuddle cup or cozy type thing you could use? If he gets inside one on his own, I'd then pick it up by the edge of the fabric (at the top/opening) so you can transport him to a cushion on your lap, hopefully without actually touching him and disturbing his scar. A scrunched up fleece or anything like that would do as a soft bed which you can put on your lap and stroke him on. Just let him walk onto it and then carefully lift him up with the fabric.
And as lovelygirl says, it sounds pretty obvious but I'd also pay extra special attention to cleaning his home. Good luck x