The dark feathering and overall mottled appearance. Only a cockerel would be so messy color-wise. Black in the leg feathering. His comb is getting a little color too. Pullets would have some tail feathers by now.
You can try listing him here, or on craigslist. Or in your local feed store...
At 7 weeks the sex should be obvious. I can tell mine by 2 weeks at the latest. Where did you get the eggs? If from certain hatchery stock it's possible to have really off colored pullets. If you can post a picture I can let you know what I think.