If you have trace levels of herpes antibodies on a IgG test, what does that mean? Does that mean you're infected with it? Can you transmit it?

Yes and yes. Igg antibodies are consistent with previous infection. Since your body never 'clears' the herpes virus once infected with it, one you have it, it is always present in your body (regardless of whether or not you have active symptoms.) you can transmit it. You are more likely to do so when you have an outbreak, but you are capable of transmitting even without active symptoms.