How much to feed a cat depends on the cat. Mine eat about 1/2 oz per pound of body weight, others on here say they feed 1 oz per pound.
Since your cat just had a dental and must eat the wet food for a week, it's a great opportunity to switch totally to the wet food. Many of us here feed Friskies pate style, Fancy Feast pate style or Wellness grain-free canned foods. All nice low carb options, under 10% which works well for diabetic cats and helps to control the glucose levels.
It's better to spread out the food into multiple mini-meals over the course of a day. Less taxing on the pancreas and helps to even out the swings in BG (blood glucose) levels.
Mine get fed 4 times a day which works well for me and my schedule. Some people freeze the wet food, and leave out a portion when they go to work. Gives the cat something to nibble on during the day. Doesn't work for me, since 2 of my civies are real Hoovers and gobble up the food in minutes.