When I had Dexter neutered I suffered from some similar problems it sounds like you're suffering from. When Dexter was returned to me his scrotum area was SO SWOLLEN!!! It was black and blueish color and looked absolutely painful. A week or so after neutering I started feeling what felt like a testicle. I was absolutely positive that is what it was and that there was something still in his little man area that they didn't probably remove.
However, a trip to a new vet revealed that the original people that neutered him just rushed to much with the surgery. Their rushing caused the extra bad swelling, and that is why it felt like there was a testicle still in there. However, it was nothing and after about 3-4 weeks of healing everything went back to usual. There was no more "round" feeling object in his scrotum and there was no more swelling.
I'm not saying that this is the case with chewbacca, but it very well may could be. Definitely get the second opinion... because it has happened where vets make mistakes and don't properly remove everything ... but to me, it just sounds like you're suffering with some very similar problems that I did with Dexter.
Hoping for the best for your little baby
I would hate for him to have to go through surgery again!