I agree that it's normal to be gone for 12-13 hours a day in a great many fields. My husband works 70+ hours a week on overtime (which happens frequently). But - I'm home to take care of our dogs.
What isn't normal is getting a little puppy, knowing in advance that you'll be away 12-13 hours a day. 18 weeks old is far too young to be left all alone for 12-13 hours. Since you already have the puppy, I would see if you can hire a dogsitter, or a very reputable doggy day care. An older dog I can see someone doing that, as they enjoy lazy days anyway (at least our senior does)...but not a puppy.
With regard to your working out after work - can't you reschedule your gym time for a time later in the evening, so you can get to your pup within the 10 hours you listed prior to working out? There are a lot of things you can do at home to work out, including playing with a puppy.
I'm not the most physically fit person under the sun, but playing with a new puppy is definitely a solid work-out for a human.
There's really nothing you can do in this situation if your schedule continues to be the same. That little pup is bored out of his mind, and quite frankly, I'm surprised he's not eating your bathroom's baseboards yet.
I agree with the other posters who said you cannot train a puppy to do something if you're never home to do it.
...if that is putting my "judgmental hat on" then oh well. When you pre-accuse people of wearing judgmental hats, it means you were fully aware that your post would raise eyebrows.
That puppy needs more attention than what you are capable of giving him.
It's unfortunate you're so far away (you are a 3 hour drive from me). That being said, if you're willing to commute an extra 3 hours before work and after work I would be happy to watch your puppy for you for free while you're at work (if he has all his shots and an up-to-date vet record).