You little guy will does just fine.
Hot Rod was just under 4 lbs when he was neutered at 6 1/2 mos. He also had teeth extracted at the same time. He was kinda out of it for 3 days but then rearing to go.
I would recommend asking your vet about pain meds and when you can give him some if needed. some procedures are done early and some late...depending on when he's done will determine if you can give him additional meds, should he be in pain. Hugs. He'll be great!