I'd say it's way too little to be honest. What weight are you trying to get him down to? I'd be feeding him somewhere in the middle probably about 200grams if he was my dog
You'd balloon Pepper then! Her food gives similar reccomendations... I give her 80-100g per day (if she's having an all dried food day/before I started giving meat each day, she usually have 50g dried 100g meat) and she still sometimes is a little over (you can feel fat between her skin and ribs). Last weight check she was a little over 10kg
She has been spayed, which I knwo can make a difference, but even so. She's an energetic dog who, among other things, does flyball training once a week. BUT she sleeps solidly. Once she's gone not much wakes her up again.
My other dog, Kye, is almost always alert and is hard to keep weight on as he worries it all off again given have the chance!
ETA: Something that might be worth looking into is if there is a hydro therapy pool close to you. I'm going to start taking Kye for his fitness levels, but it's also a good way to loose weight
http://www.canine-hydrotherapy.org/Have look on here for a registered one