Don't be so hard on yourself, but yeah that was a boneheaded move.  The funding address would likely have sufficed.  I always got the impression that ChipMixer is a one-man operation, I could be wrong.  If so, then it really doesn't matter the owner must have full access to the wallet anyway.  Regardless, their reputation is impeccable, so I'm expect you'll be fine.

Do us a favor, and please let us know when your issue is resolved.