You'll be glad to hear there's two very simple things you can do that will most likely help a lot:
1. Stop feeding the dry food - it's bad for your cat and will cause him to gain weight and may cause diabetes, IBD, teeth problems, the list goes on..
2. Change the wet food you're feeding to a better brand, such as Hi Life 60%. Better yet, buy one of these sample packs
Raw Taster Pack [Taster] - £10.00 : Food4-Cats!, Just Food for Cats Nothing More! and you should see him tuck into his food with gusto!
There's little that brings me more joy than to see my boy tuck into his food like he really enjoys it, and since I changed him over to raw he's excited over each meal!
Good luck with yours
