Two questions actually. I have a 1 year old 80 lb black lab who is used to eating 3 times a day (3 cups a day) My wife and I leave at 7:40 and return at 5:15 or so from work. I come home between 12-2 to feed him a cup and let him out

1) How do I transition my dog to having 1 1/2 cups twice daily without freaking him out?

2) Can I leave my lab at home all day (He's crate trained) and just let him out and feed him when I get home each night?