Harley is very cute!

I would definitely recommend neutering him. No, 3 years is not too old. I've had 2 dogs that weren't neutered until they were older than 10 years and they had no problems. It's a very routine surgery and I would not call it cruel. When I brought home Nebo (my husky) home after being neutered as a pup he was bouncing off the walls, didn't act the least bit in pain.