Glad to hear the little guy is getting alot of yummy treats. =D
Some of the things my guys & girls go crazy over is:
Watermelon, Cantelope, Green Beans, Tomatoes, Broccoli, Spinach, Peas, Corn, Bell Peppers, Peaches, Blueberries, Strawberries.. and you can't forget bananas(but make sure they aren't green bananas, as thats not great for them.) Really, rats can eat a wide variety.
Do gradually introduce Winkie to new foods, as too much can be hard on his stomach. You may have to experiment with foods to see which he prefers... as with my rats, some of them might not touch something while the other rats will love it!
Things to stay away from are: Too much peanut butter. It can get stuck to the roof of their mouth and they may choke to death.

And about the orange issue mentioned above, its said to only be the orange rinds, and that some male rats have no problems with it. I wouldn't take any chances, though. The reason it only affects male rats, I believe, is because the males have a naturally occuring protein, and a certain chemical the orange rinds puts into the male rats body makes protein build up in the kidneys, normally resulting in kidney cancer. (Don't quote me on that! I may have gotten it mixes up with another fact. )

Also, yes, you can get a rat neutered. I wouldn't do it, though. I have 6 male rats and have researched it before. Males don't have as high of a chance to get tumors as female rats do, and if they do get tumors, its not testicular tumors. The only help you'd pretty much be doing by getting him neutered would be a better temperment, a nicer looking coat, & less territorial markings(resulting in less of an odor). Since Winkie already seems to have a nice temperment, and the fact that a good coat comes from a good diet and the odor comes from infrequent cleanings or an unsuitable litter, I still advise against getting him neutered.

If you have any further questions, don't hesitate to contact me.