Hi Brandy,
Unfortunately, it sounds as if you've trained Wiggles to be the picky eater that he is. By feeding him extra treats, switching his dogfood, and adding human food over the two years, you've pandered to his bad habit. Now he knows if he waits you out, he'll get something special.
The only way IMO to fix this is to wait him out. If he's healthy, he will not starve himself. Might get a little lighter, but he won't starve away to naught.
BTW, do you give him his food once/twice a day or is it sitting out all day long? Sitting out tends to encourage picky eating. The buffet is always there ;)
Put the food down at breakfast/dinner time for about 15 minutes. If he doesn't eat (and stay at his bowl--don't let him take the food away to eat somewhere else), pick it back up and give it back to him at the next scheduled feeding time. Ditto until he eats what you feed him. Cruel sounding, but realistic.
***********************************
Dealing with the puppy is another problem. By playing with Wiggles extra, you're actually doing ok. Take Wiggles out on walks by himself (that will help with appetite, too). When dinner dish is being put out, his goes down first. Treats ---he gets his first. Get the picture? :D
But also exercise them together. Get him accustomed to not being the only dog anymore. Make sure that Wiggles and RU eat separately...each has his/her own place/bed, toys, etc... You didn't give the breed of RU, hopefully, she'll be just as small--- eventually, she'll likely end up the boss...but that's in a while.
When visitors come over, have them pay attention to Wiggles first, puppy second. BUT you have to emphasize good manners and protect the pup. Each has to have their own bed...if Wiggles sleeps with you, puppy stays down. But if you want them both up on the bed, as soon as Wiggles gets upset ....both dogs are ejected.
Anytime he growls or gets bossy, you tell him "no" and eject him from whatever is going on. He starts biting... "no" then you ignore him/send him to his bed..etc.., and continue playing with puppy. You're the boss and you will not tolerate bad behavior :D
Don't let them be alone together without supervision for quite a while. It might be that he will never like her and you might have to permanently separate them. But in the meantime....
Let Wiggles know, that you will favor him over Ru, but only on your terms :) He can sit politely when it's her turn. It sounds as if he's smart enough to understand that he'll always be first, but only when he behaves. :D
I hope this helps you out a little. Good luck
toodles