Helping a dog sleep longer in the morning?

I have a 6 month old male yellow lab who has been waking at 4:00-4:30 every morning for the last two weeks. For context, I’m typically up at 5:00 for work every morning. He will get up with me, go out and go potty, and then chew on a bully stick or another chew while I get ready for work. We then go back downstairs, and he relaxes on his bed in the corner or on the kitchen mat until about 5:40-6:00 AM when I put his food down in his kennel and go to work. He will then sleep until about 6:45 or 7:00 when my fiancé gets up. He hangs out with him and then goes into the kennel for the day at 7:45 or 8:00 AM. My fiancé says he’s pretty tired in the morning and doesn’t have a ton of energy. He will sleep all day in the kennel. He gets a frozen Kong in the morning and then one again when he goes back in at noon-1:00 after our dog sitter stops by to let him out, feed him, and play with him. This 4:00 AM wake up call happens even if he gets enough stimulation in the evening or throughout the day. I’ve tried letting him cry it out, but that was 45 minutes of barking and crying. I’ve tried letting him out and putting him back in, which only seems to work for about 15 minutes before he’s crying/barking again. I’ve also tried feeding him twice in the evening (half of his food around 6 and the other half around 8). Should I continue to just let him air his grievances? Any other tricks I should try?