Please get the vet out to your place tomorrow. I am afraid you're totally over your head with this horse. Please realize I'm saying this without any ill will. People have given you ideas about diet but you can kill your horse if you change his diet quickly.
How did you determine what to feed your horse? The foods you're feeding are not usual horse diets. Most people feed hay diets. In the summer, good grass may be all that's necessary. Please be very careful at changing your horse's diet. You don't want him to colic or founder.
I have a chronically ill child. I know that at times I've not been able to look at her and tell how skinny she was. Because I knew that this was tough I'd look at her in pictures to tell how she was doing. There's no doubt that this horse is in serious trouble.
I would guess that you don't have a lot of horsey experience. If you're having these issues with feed, I'd bet that you're also having or headed towards training issues. Do you have an instructor? Do you take lessons? Do you keep your horse alone?
Again, I am not trying to sound mean but please call the vet in the morning. Please consider getting some serious ongoing assistance with your horse.