You'll lose most of the aromatics from the honey if you boil it. If you add it late, or add it to the secondary, you should be able to carry some of the honey flavors through to the finished product.
IME, honey flavors are delicate regardless of how you add it and they may not come through in a porter. Especially a chocolate porter. Personally, I would still add it at knock out, but I'd probably cut back from 1lb to a 1/2 lb or so. I'd up the orange zest if you were planning on orange from the honey. No harm in increasing the MO to balance the gravity lost from the honey.