I have met quite a few people who have out of control German Shepherds, whether its running away, biting, or barking etc. These people were in the suburbs and the dogs probably didn't get enough exercise. We had a German Shepherd and I took him to training which helped. One thing which calmed my dog down was after going for a long walk. I know its difficult for you as I also found it a full on job. I agree that getting him desexed will help.
What exactly is a check chain? Is that the same as a choker chain?
Anyway, since you are not in the suburbs you can let him run around loose, he wouldn't need tying up ??
Another suggestion, maybe get him a companion, so the two dogs can keep eachother company and won't get so lonely or bored when you are at work.
Good luck!!