Just remember after fixing the leak there will be more oil from that leak still making it's way to the ground. (unless you cleaned it really really good) So it may just be that oil getting to the end if it's trail. The crank sensor is easy to check and replace though if you are hunting a leak. As for the x-member and all that is likely from that rear main, as it will also leak where the inspection plate is, where the bell housing meets the block. So get the rear main done as soon as you can. The wind will whip all that oil around under there though so it will get onto the cat and the underside of the unibody under the fire wall etc, it will blow everywhere.. Good luck bro I've chased leaks before and I know it stinks!