I'm sorry to be a dissenting voice here, but I still think it's possible to encourage Preet to see your home as his base, return to you at night and for food, but be allowed outdoors to play and occasionally visit someone.
I think that the ways to do it are:
Keep him in for a month. You only kept him in for 2 weeks, this isn't long enough to bond a new cat to you. It was long enough for him to recover from the operation, but not to tell him you are mum and dad.
Talk to your neighbours. I have a neighbour who used to feed my cats, I had to have several talks to her to stop this. They were disappearing, not eating when home (so I worried whether they were ill, or had been fed already).
The reason why I think it would be good for him to be more domesticated is that it will be easier for you to spot when things aren't right with him. If too many people feed him, how will you know he's off his food. How will you know that he isn't being double treated for worms or fleas? This could be dangerous.
He may, in the future, require pills which have to be given at certain times (like antibiotics), how will you be able to find him at the right time?
Many people on this site prefer cats to be kept in at night to prevent car accidents. How can you do this?
I see your point about him being a free spirit, but I don't think it's in his best interests long-term. While he's well, young, and healthy, this probably won't be too much of a problem. But what about when he gets ill, or older?
I'm just throwing into the discussion the way that I see this situation and what I would do.
Love to Preet