Crating him at night and while you are working won't kill him or ruin his personality. He's 6 months old. My guy is 6 months old and still sleeps downstairs in his crate because he can't stay still upstairs in his crate yet. He spends the night in the crate and roughly 4-9 hours in his crate during the day depending on our schedule. I'm a stay at home mom but I'm kept pretty busy out of the house with various appointments and errands. Neither of my dogs have suffered for it.
Exercise physically helps but exercise mentally must also be in there. A dog is going to get worn out mentally and able to settle better far more than being worn out physically. Same goes for people. You have trouble sleeping because you can't turn your mind off to do it. You're physically worn out but if your mind is just going and going, you're not likely to get much sleep.
Lots of short training sessions throughout the day you're with him as well as physical exercise and crate him at night should help him learn to settle down more easily at bedtime.
And crate time is broken up during the day for potty breaks. its rare I'm gone the entire day.
The more people I meet and talk to,the more I love my dogs and their intelligence.
Shasta GSD 5/5/10 CGC
"Dax" Thor z vom Weberhaus 3/18/2013
Zena GSD 6/1/03
Riley GSD/BC 1/10/05-2/1/2013