Feeding Pete (a never-ending story)

I’m really struggling to work out how much to feed Pete. The shelter said they gave him a wet pouch and biscuits twice a day. The day after I got him, I took him to the vet for jags and check-up. The vet weighed him and said 5.8kg was fine. I’ve been giving him a pouch when I get up and 20-25g biscuits when I leave for work, a pouch at teatime, and 20-25g biscuits when I go to bed. And if he’s been a really good boy, he gets a couple of Dreamies, and now and again I defrost a couple of prawns as a treat for him. He gobbles the pouches down in seconds and asks for more, and when I put the biscuits down, he gobbles about 3/4 of them and eats the rest little by little. But he seems to be hungry so much of the time, he spends a lot of time meowing for food, winds round my feet hopefully as soon as I go near the kitchen and tries to eat anything left out on the worktop that looks likely. And when he doesn’t get anything he lies down next to his bowl and looks sad. I don’t want to over feed him, especially just now when he’s not getting much exercise, but I don’t want to starve him. I gave him 30g biscuits this morning after his wet food and he ate most of them and has been snoozing contentedly ever since.

He’s a big strong cat, but he’s not fat, and you can feel but not see his ribs along his sides. How do I tell if he’s genuinely hungry and needs food, or if he’s just being greedy? We’re going back to the vet next week for his next jags so I’ll ask them to weigh him again and have a chat about the lower and upper limits of what to feed him.