Concern over how cat is being fed

Hello.

I have some questions about how a cat should be fed. for a background, this is not my cat but it is my landlord’s daughter’s cat that she just adopted at the start of this year. ever since we got him, a now 3 year old male cat that’s average in size, she has been saying that she wants him to be “small like a kitten“. She tried to feed him less, as in one 84 calorie/3 oz wet food can per day, but I thought this wasn’t right since he isn’t overweight or anything. I could tell he was very frustrated so I convinced her to go back to feeding him dry food and wet food and his mood improved a lot once that happened. In addition, she has started skipping feeding him all together without telling anyone. Now, she is feeding him 15 grams of dry food in the morning and a 84 cal/3 oz can of wet food at night. The bag of dry food suggests 53 grams or 1/2 cup for an adult cat around 10 pound, which is the weight we think he is.

My two questions are: is 15 grams of dry food and one 3 oz can of wet food enough for an adult male cat of average size? And, if a vet somehow told her that he’s overweight, would they perhaps recommend cutting his food intake by that much?