I am sorry to hear you are worried about Pounce. My name is Rebecca. I am a veterinarian and will do my best to help.
When a cat stops eating, it is often the only way they can tell us that they are sick, painful, or have problem. Since he is also licking his penis, that is one other clue to what is wrong with him. It is normal for a cat to vomit hair balls, that is part of normal maintenance: they groom themselves, and from time to time have to vomit hair that does not pass. It is rare for hair balls to make a cat stop eating.
I am worried about his licking his penis. He may have cystitis, a bladder infection and it burns or stings when he urinates causing his discomfort. However, a more serious problem in young male cats is a urinary blockage in the penis, and he can't urinate. The urine builds up in the bladder, is very painful, and these cats stop eating, and sometimes start to vomit. If the blockage is not corrected, they can get very sick. Is he passing any urine, can you tell?
If he were my own cat or my patient, I would palpate his bladder and if the bladder is enlarged, firm or painful, I would pass a catheter to remove the blockage and get him urinating. If the bladder is small and there is no blockage, I would get a sample of his urine to see if he has cystitis, or crystals in his urine.
He is telling you the only way he can that something is wrong and the only way to get him eating is to find the problem and correct it. Really monitor him to see if he is passing urine and if he is not, get him to your veterinarian as soon as possible. Until then, try to keep him hydrated by offering water, broth, tuna water, anything to get some fluid and nutrition into him.
Let me know how he is doing and what other questions you have. Rebecca