Hello and Welcome !
I'm not a food expert by any means, but I saw that no one else had replied to this yet, so I figured I'd give it a shot.
It looks like Nutro cups are the standard 8oz. with a feeding recommendation is 4 1/2+ cups per day for his weight.
For your dog's weight, the Wellness feeding guidelines show 4 - 5 cups per day; however, Wellness cups are 4oz. So that would be 18oz. of food per day with Wellness if you stuck with 4 1/2 cups as the amount vs. 36 oz. per day with Nutro. With Wellness there is probably a smaller amount of fillers used, and the nutrients are more densely packed, allowing you to feed the smaller volume.
For the amount, I think 2 times a day would be better than 1. I don't know if the same applies for dogs, but I"m just thinking of with humans when you diet, you want to do multiple small meals to keep the metabolism up.
Just another thought, there is a Wellness Lamb & Rice formula, but maybe taking some of that rice meal out would help with the weight loss. The Super5Mix Chicken or Fish & Sweet Potato might be a better choice.
Good luck !