I think solid ground work can be so much harder to teach than ridden work, especially for a beginner. Plus with history of being a bit bolshy and as a novice yourself I think his ground work looks great. He's backing up nicely, with no pressure and lovely and straight.
The hanging basket made me laugh, my mare would have been exactly the same.
Agree with chunkiness. My mare gets honeychop lite and healthy which is low sugar and added bonus of no alfalfa. If Prince isn't bothered by alfalfa then their plain oat straw chaff is even better, it's got puny amount of sugar in so like others have said you can fill him up on that. Or topchop zero I think is the lowest of them all.
As for them being angry, they will eventually get over it. My mare used to get breakfast and dinner and this winter when I stopped dinners and she came in from the field and couldn't find her feed bowl in her stable ready and waiting she hit the roof. This carried on every day for a ridiculous amount of time but now she goes in and just munches her hay instead. I can even make her breakfast now outside her stable and she doesn't scream at me. This is a mare whose sole purpose in life is to eat. Horses are creatures of habit but give them enough time and they will eventually break those habits!
I see he is clipped, does he go out rugless? If he doesn't I'd start whipping rugs off, it's a lot milder now and the more calories he can burn the better (I can't remember if he is in work?). Going rugless has been a complete game changer for my naturally porky native.
To be brutal, it is far more painful for a horse to develop laminitis than to get a less tasty dinner/less dinner.