Have you tried putting the crate inside the expen? I use that method with distressed or young puppies because they hate being exposed. I think the expen makes them uncomfortable because it places them in a vulnerable position: they have nowhere to run and no shelter to hide in. To help with this, I also use a cover for the expen.
If his food, toys and crate is in there, he will learn to love it very quickly! When it is bed time, I throw a cookie into the expen/crate, making sure that the puppy sees it. And then, when he goes in there to get it, I slowly close the door. Make sure it is a big cookie to keep him busy for a little while
This method has worked very well for all my own dogs and the puppies I foster for welfare. A dogwalker/dogsitter is a great idea for when the puppy is older. You have to accept that the puppy is growing to cry because all puppies do, but if you react and give him what he wants when he is barking, he will continue to do it. Often, it only takes one day (or night) for the puppy to realize that barking/crying doesn't help. I always pretend I can't hear these sounds and I turn away if they start crying or barking. I never open a crate or expen door if they are crying/barking - it reinforces the bad behavior. I wait until they are silent, however long it takes, before I let them out. If they continue barking, you just turn away.
I hope I don't sound harsh, but I had a dachshund growing up and he wouldn't stop crying and barking when he wanted attention. My parents gave him away because of it, so I am very strict with my dogs about it.
I hope that helps!