Crating at night...
At this point you aren't going to be able to tell when he's crying just to be let out of the crate or when he needs to relieve himself. Once he's used to the crate, then when he cries you'll know he actually needs something. For now you have to ignore him except for when you think he needs to go. Usually it doesn't take
that long for the crying to get out to stop. Try putting something in the crate with your scent on it. The crate actually becomes a place they like when done right.
He may or may not ever be able to hold it the entire time you are at work. Gus is almost four years and most days needs to relieve himself about every four hours, some days more often.
When crate training, you are supposed to be home most of the time. You have to be there to let them out when needed or they will go in the crate and then you aren't teaching them anything. It can make it even worse. That's one of the reasons pet store puppies can be so difficult to housebreak.
I agree with the vet, I would keep him in the bathroom with a pee pad, toys, water and food...you are gone too long for him not to have any food. It could cause hypoglycemia, which can be deadly for these tiny puppies.
At this age (and probably for months yet) they give very little warning so you must watch them very closely when running free and take them out a lot. The more accidents he has in the house the harder it is for you to get through to him that's not where he's supposed to go.
Good luck. Like the others have said, it takes time, persistence and patience (and then some more time, persistence and patience!). And maybe some caffeine to stay awake during the day.
