The odds of this being a scam are pretty high i'm afraid... In my experience, at least 90% of the darknet hidden services are a scam in some form, and the ones that aren't are usually reviewed and published on a lot of forums, blogs, reddit,...
I hope you didn't lose to many coins, next time remember: if you're not (the only one) in controll of your private keys, you're not (the only one) in controll of your coins! There are perfectly good tutorials on how to use electrum over tor, i suggest you use those ones.