Is there anyone that can come home at lunch at let him out - or on break?
It sounds like if he gets what he's supposed to do, which is fantastic btw. You probably shouldn't train him to go in his kennel if no one is home, as that's the exact opposite of what a kennel is supposed to be. It's supposed to be their bed, and you wouldn't go in your bed?
Another alternative you could look into if no one can take a break to come home would be some kind of doggie day care. I used to do this with one of my dogs who had issues if left home alone. Many kennels and some vets have a doggie day care where for usually around $5-10 you can leave your dog with them while at work every day.
High - 281
Current - 252
Low - 159 (2012)